Intervertebral disc (IVD) degeneration is strongly associated with back pain, and affects approximately 60% of the population by age 70. Furthermore, it has been suggested that this degeneration may play an important role in the initiation or perpetuation of vertebral fractures. Given that the IVD is a primary load-bearing structure in the spine, the change of intradiscal pressure (IDP) over time that accompanies disc degeneration provides a functional measure of the disease pathology. Studies show that both an overall decrease in IDP magnitude and changes in the spatial distribution of IDP are found with increasing levels of degeneration. Thus, the overall goal of this study was to determine the correlation between the spatial distributions of IDP, as measured along both mid-sagittal and mid-coronal paths, and a clinically feasible assessment of disc health. Disc degeneration was assessed non-invasively using quantitative computed tomography (QCT). A custom, electro-mechanical device was designed, manufactured and assembled to measure IDP distributions. The results indicated that the spatial distribution of IDP was most homogenous for the nucleus pulposus (NP) region regardless of load type and disc health grade. Mean IDP tended to be lowest in severely degenerated discs, consistent with earlier findings that axial loads in spinal columns with degenerated IVDs shift from the disc to the neural arch in both flexural and erect postures.

The emergence of limbs in vertebrates represents a significant evolutionary innovation. Limbs facilitate diverse motor behaviors, yet require spinal networks that can coordinate the activities of many individual muscles within the limb. Here I describe several efforts to characterize the specification of spinal motor neurons and assembly of spinal circuits in higher vertebrates. I discuss the formation of selective presynaptic sensory inputs to motor pools, a process which has long been thought to occur in an activity-independent manner. I demonstrate an as yet unappreciated role of activity-dependent refinement in patterning the set of sensory-motor connections that link motor pools with synergist function. I also explore the genetic specification of motor pools that project to defined muscle targets. I show that the motor pools that control digits engage distinct developmental genetic programs which reflect underlying differences in Hox and retinoic acid signaling. The divergent mechanisms underlying the specification of digit-innervating motor neurons may reflect the unique status of digit control in the evolution of motor behavior.

For the nervous system, there is evidence of relative shortening of the spinal cord, reflected by both reduced cord length to vertebral column ratio and a change in cross-sectional morphology of the cord. The cerebellar tonsils are low-lying in AIS subjects while significant regional volume differences in the brain are also evident between AIS subjects and controls. / From the results of this series of study, AIS girls are found to have morphological difference in multiple aspects when compared with age- and sex-matched normal controls. / Idiopathic scoliosis is a common worldwide problem and has been treated for many decades; however, there still remain uncertain areas about this disorder. Its involvement and impact on different parts of the human body remain underestimated due to lack of technology in imaging for objective assessment in the past. / In the skeletal system, AIS girls have generalized osteopenia and abnormal growth of the appendiceal skeleton. For the axial skeleton, abnormal ossification patterns have been found affecting both the longitudinal growth and axial growth pattern of the vertebral column. There is overgrowth of the anterior vertebral column, reversed asymmetry of the neural arch and smaller pedicle at the concavity of the scoliotic curve in AIS, suggestive of asynchronous growth between membraneous and endochondral ossifications. In the skull, both calvarium and basicranium are found have regional difference (including foramen magnum) between AIS subjects and controls, which is again probably reflecting a systemic process of asynchronous growth between membraneous and endochondral ossification. / It was concluded that the hypothesis "In adolescent idiopathic scoliosis, advanced magnetic resonance imaging techniques can be used to identify systemic features which are suggestive of asynchronous neuro-osseous growth of the disorder" was confirmed. (Abstract shortened by UMI.) / Taking together, the abnormalities in the skeletal system and nervous system are likely to be inter-related and reflecting a systemic process of asynchronous neuro-osseous growth. The above findings help to explain a number of well documented neurological abnormalities in AIS: Anatomically, there is increased incidence of Chiari malformation and syringomyelia in AIS subjects, while functionally, abnormal somatosensory evoked potential (SSEP) results, impaired postural balance, poor performance on combined visual and proprioceptive testing and spatial orientation testing as well as reports of abnormal nystagmus response to caloric testing are known to be associated with AIS. / The advances in imaging technique and image analysis technology have provided a novel approach for the understanding of the phenotypic presentation of neuro-osseous changes in AIS subjects as compared with normal controls. Dynamic imaging also assists in functional assessment of pulmonary function and respiratory mechanism in AIS subjects. / The hypothesis to be tested in this series of studies is: "In adolescent idiopathic scoliosis, advanced magnetic resonance imaging techniques can be used to identify systemic features which are suggestive of asynchronous neuro-osseous growth of the disorder". This thesis was based on a series of eight studies which were aimed to explore the "unknown" anatomical features in the skeletal and neural systems in AIS by the application of new advanced technique of MR imaging and sophisticated image analysis programs. / We are the first group who has undertaken a comprehensive morphological assessment of the skeletal and nervous systems in AIS subjects based on imaging findings which have not been reported previously. For the first time in literature, the spinal cord and vertebral column, brain and skull were thoroughly analyzed in AIS subjects and compared with age- and sex-matched normal controls. Detailed correlations with clinical information, neurological tests have also been made. As an appendix, MR imaging findings of the pulmonary system in AIS, including the lung, chest wall and diaphragms are also presented at the end of the thesis. / Chu Chiu-wing, Winnie. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0976. / Thesis (M.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 248-267). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / School code: 1307.

Disc degeneration is a natural process and is widely prevalent. The severity of disc degeneration and the type of treatment varies from person to person. Fusion is a commonly chosen treatment option. However, clinical and biomechanical studies have shown that intervertebral discs adjacent to a fusion experience increased motion and higher stress which may lead to adjacent-segment disease. Cervical disc arthroplasty achieves similar decompression of the neural elements, but preserves the motion at the operated level and may potentially decrease the occurrence of adjacent segment degeneration. Computationally, a validated intact 3D finite element model of the cervical spine (C2-T1) was modified to simulate single (C5-C6) and bi-level (C5-C7) degeneration. The single level degenerative model was modified to simulate single level fusion and arthroplasty with the Bryan and Prestige LP artificial discs. The bi-level degenerative model was modified to simulate a bi-level fusion, bi-level arthroplasty with Bryan and Prestige LP discs and a disc replacement adjacent to fusion. An in-vitro biomechanical study was also conducted to address the effects of arthroplasty and fusion on the kinematics of the cervical spine. A total of 11 specimens (C2-T1) were divided into two groups (Bryan and Prestige LP). The specimens were tested in the following order; intact, single level TDR at C5-C6, bi-level TDR C5-C6-C7, fusion at C5-C6 and TDR at C6-C7 (Hybrid construct) and finally a bi-level fusion. The intact state was tested up to a moment of 2Nm. After surgical intervention, the specimens were loaded until the primary motion (C2-T1) matched the motion of intact state (hybrid control). In all cases; computational and experimental, an arthroplasty preserved motion at the implanted level and maintained normal motion at the nonoperative levels. A fusion, on the other hand, resulted in a significant decrease in motion at the fused level and an increase in motion at the un-fused levels. In the hybrid construct, the TDR adjacent to fusion preserved motion at that level, thus reducing the demand on the other levels. The computational models were used to analyze disc stresses at the adjacent levels and facet forces at the index and adjacent levels. The disc stresses followed the same trends as motion. Facet forces though, increased considerably at the index level following a TDR. There was a decrease in facet forces however at the adjacent levels. The adjacent level facet forces increased considerably with a fusion. The hybrid construct had adjacent level facet forces between the bi-level TDR and bi-level fusion models. To conclude, this study highlighted that cervical disc replacement with both the Bryan and Prestige LP discs not only preserved the motion at the operated level, but also maintained the normal motion at the adjacent levels. Under hybrid loading, the motion pattern of the spine with a TDR was closer to the intact motion pattern, as compared to the degenerative or fusion models. Also, in the presence of a pre-existing fusion, this study shows that an adjacent segment disc replacement is preferable to a second fusion.

Lumbar degenerative disc disease is a remarkably common condition among patients presenting with chronic low back pain and physical disability. When a surgical treatment option is warranted, patients now have the option of undergoing lumbar total disc replacement (TDR), a relatively new procedure that is designed to replace lumbar fusion, the traditional surgical intervention for degenerative disc disease. The lumbar TDR procedure has demonstrated clinical efficacy equivalent to that of lumbar fusion, although concern remains about the longevity, safety, and costs related to the procedure. These issues were addressed in three separate observational studies using administrative claims data. The first study estimated the revision burden and economic revision burden of lumbar TDR. The second study examined the lumbar TDR hybrid procedure, where both a lumbar TDR and lumbar fusion are performed simultaneously. No observational data have been reported on the frequency, cost, and diagnostic indications related to the TDR hybrid procedure. The third study mapped the geographic variation of procedural rates of lumbar TDR. Previous research has found substantial geographic variation in lumbar spine surgery rates and a similar analysis of lumbar TDR variation has yet to be reported. The present series of studies found the revision burden and economic revision burden of lumbar TDR to be similar to data reported for this procedure from the mid-2000s, though the overall occurrence of the procedure appears to have declined. The economic revision burden made this a lower-cost procedure than lumbar fusion, with a tradeoff in terms of revision burden being higher for lumbar TDR. The lumbar TDR hybrid procedure was found to make up approximately 16% of the total number of TDR procedures, involving much higher costs than a single-level TDR procedure. Finally, geographic variation of the procedural rate of lumbar TDR varied dramatically across the U.S., surpassing the variation observed in lumbar fusion surgery. Limitations of the observational data used in these studies are described. Recommendations for future observational research are offered as well. Finally, implications for these studies on practice guidelines and reimbursement policies are provided.

80% of the American population experiences back pain and it is the most common cause of limited activity in people of age 45 and under. Determining the reasons for back pain and developing new ways to treat it have been extensively researched over the past decade. However, very little research has been done on low back pain of amputees. There are four million existing amputees living in America and 250,000 people become new amputees each year. 70% of this group is lower limb amputees and a large number use a prosthesis of some kind to aid in the functions of daily living (Amputation and Limb Deficiency). Not all amputees use a prosthesis because of pain involved, aesthetics, and cost. In order to increase the use of prosthetics among amputees, the reasons why they do not use them must be fully understood. With this knowledge better prosthetic designs can be created. The purpose of this study is to first determine the prevalence of back pain among lower limb amputees who use a prosthesis and then to quantify the accelerations in the spine of this group and compare it to subjects who are not amputees. The findings of this study will be used to determine if back pain is a common complaint, if it interferes with daily activities, and if the use of a prosthesis causes abnormal loads in the spine of amputees. A cross-sectional descriptive survey was created and distributed to lower limb amputees who use a prosthesis and to a control group. In addition to the survey, several subjects were recruited to wear an accelerometer located over the L5-S1 vertebrae and walk at several speeds down a pathway. A maximum acceleration was determined for each step as well as the difference in acceleration between opposing legs. Also measured was the effect of a leg length discrepancy (LLD) on accelerations and back pain. As a result of this research it was found that a high percentage of amputees experience back pain and the prevalence is higher than that of controls. It has shown that there is a difference between the acceleration patterns of amputees and non-amputees, but further research is needed to show that this difference is what causes the higher prevalence of back pain. The trend of side dominance and its increase with increased walking speed for amputees has been shown as well as a general population trend of increased acceleration of the spine with increased speed. In relation to walking speed, the study has also shown that the perception of speed among amputees is slower than that of controls. This study has also supported the notion that a difference in leg length could cause low back pain.

No description available.

Abstract not available

The thoracolumbar transversospinal muscles are vital in normal function and are implicated in the pathogenesis of different forms of spinal pathology and pain. They are the target for specific forms of clinical intervention such as exercise regimens and the release of �trigger points�, and are often analysed through imaging studies and electromyographic recordings. Despite the importance of these muscles, there is a paucity of knowledge in regard to aspects of their functional morphology. The aim of this thesis was to examine the thoracolumbar transversospinal muscles between the mid-thoracic spine and sacrum, examining their gross morphology, fibre arrangement, fibre types, and an animal model in order to provide a better understanding of their functional morphology. The gross morphology of these muscles was studied by micro-dissection of cadaveric material. Their form was found to differ from that published in either text book or peer reviewed articles, clearly indicating the existence of a �semispinalis� muscle in the lumbar spine. In addition, the arrangement of these muscles was found to be homologous between the thoracic and lumbar regions, which is contrary to published descriptions. Arrangement of the muscle fibres was examined by identifying motor endplates with acetylcholinesterase histochemistry in all muscles throughout the area of interest. Only one endplate per fibre was observed, and no in-series fibres were found. All muscles showed a complex multipinnate form with large areas of muscle tendon intruding into each muscle. Fibre type proportions in each muscle were investigated by immunohistochemistry. Results indicate the percentage of total muscle area occupied by type I fibres decreased the more caudad the vertebral level of origin, for all muscles. There were significant differences in the area percentage of type I fibres between many different vertebral levels. These differences were mostly found between the most cranial and most caudal levels examined. The percentage of type I fibres recorded suggest all muscles are likely postural in function, and the gradual decrease in type I fibres and the lack of a distinct thoracic / lumbar boundary in the data suggests the thoracic and lumbar transversospinal muscles are homologous. The thoracolumbar transversospinal muscles of the MLC3F nlacZ transgenic mouse were micro-dissected to determine their morphology, and their fibre arrangement subsequently determined using acetylcholinesterase histochemistry. These muscles showed a homogeneous form throughout the thoracolumbar spine, and no in-series muscle fibres were observed with all muscles having one motor endplate per fibre. Results indicated similarities between the morphology of mouse and human transversospinal muscles, perhaps indicative of an adaptation to an upright posture. This thesis provides information that facilitates a more complete understanding of the morphology and function of the thoracolumbar transversospinal muscles. In addition, results indicate that these muscles are homologous through the thoracic and lumbar spine, and therefore the classification and nomenclature used to describe these muscles should be re-examined. Furthermore, the morphological evidence, combined with recent embryological studies, supports the use of the term �spinotransverse� to more accurately describe this muscle group.

Pedicle screw breakage and loosening remain as clinical complications of short segment instrumentation procedures for spinal stabilization. This study has directly visualized and measured elastic, plastic and total vertebral pedicle trabecular bone full-field strains in the regions immediately surrounding the pedicle screw during pedicle screw insertion by utilizing functional microCT imaging and digital volume correlation. Human, porcine and polyurethane foam samples were analyzed and compared. Analysis showed that when osteoporotic human, normal human and porcine pedicle trabecular bone samples were compared, osteoporotic samples showed higher peak plastic strains and greater variability of these strains from their means. This suggests that osteoporotic human samples are non-uniformly elastic and plastic, while normal human and porcine samples are more uniformly elastic and plastic throughout the trabecular structure. PU-foams are not appropriate as models for pedicle trabecular bone in the in vivo environment since strain results showed dissimilar plastic and elastic strain magnitudes than human and porcine pedicle trabecular bone. This study may aid in the development of performance criteria for new PU-foams and improved pedicle screw designs. / Graduation date: 2004