The spine journal : official journal of the North American Spine Society
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Painful lumbar disc degeneration is one of the most common ailments treated by spine surgeons. Currently, early disc disease and herniation are often treated with microdiscectomy. Late disc degeneration is usually treated with arthrodesis. With the advent of new technology and techniques in lumbar disc arthroplasty, interest in preserving spinal motion at degenerated motion segments has increased. The goals of lumbar disc arthroplasty are to provide long-term pain relief at the degenerated disc level, to restore disc height to protect neural elements and to preserve motion to prevent posterior facet arthropathy and adjacent segment disease. ⋯ Short-term results of lumbar disc arthroplasty as measured by pain relief and disability are good in some studies. Implants are relatively safe in the short term, and with newer designs complications are usually related to the surgical approach rather than early implant failure. Recovery times appear to be shorter than arthrodesis. Despite the relatively good early clinical results of these devices, questions remain about the long-term efficacy in pain relief and maintenance of motion, the results of randomized comparative trials with fusion and the life span of the devices. In addition, late sequelae and revision options are unknown. Current indications for lumbar disc arthroplasty are in the setting of a Food and Drug Administration trial in young, nonosteoporotic patients with one or two level symptomatic disc degeneration without severe facet arthropathy, segmental instability or neural element compression requiring a posterior decompression.
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Comparative Study
Presurgical biopsychosocial factors predict multidimensional patient: outcomes of interbody cage lumbar fusion.
Interbody cage lumbar fusion (ICLF) has been advanced to improve arthrodesis; however, little attention has been given to quality of life and functional outcomes. Studies suggest that psychosocial factors may be important modifiers of low back surgical outcomes. ⋯ Overall, despite a high rate of arthrodesis, ICLF was not associated with substantial improvements in patient functioning. Presurgical biopsychosocial variables predicted patient outcomes, which may help improve patient selection and possible targeted interventions.
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Comparative Study
Biomechanical changes after the augmentation of experimental osteoporotic vertebral compression fractures in the cadaveric thoracic spine.
Osteoporotic compression fractures are an important public health concern, leading to significant morbidity, mortality and economic burden. Cement augmentation procedures used to treat these fractures alter the biomechanics of the fractured segment, which could promote adjacent failure. However, if alignment is improved or restored, there will be less risk of adjacent failure. ⋯ With axial compressive loads, the addition of flexion increases fracture risk. Cement augmentation of a fractured vertebral segment reduces stiffness while increasing both the superior and inferior adjacent cortical strain. This increment in strain that is greatest on the inferior adjacent vertebra effectively redistributes loads from the superior adjacent vertebra to the inferior adjacent vertebra, sparing the superior adjacent vertebra from failure.
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In patients with osteoporosis, changes in spinal alignment after a vertebral compression fracture (VCF) are believed to increase the risk of fracture of the adjacent vertebrae. The alterations in spinal biomechanics as a result of osteoporotic VCF and the effects of deformity correction on the loads in the adjacent vertebral bodies are not fully understood. ⋯ The anterior shift of the compressive load path in vertebral bodies adjacent to VCF can induce additional flexion moments on these vertebrae. This eccentric loading may contribute to the increased risk of new fractures in osteoporotic vertebrae adjacent to an uncorrected VCF deformity. Bone tamp inflation under a physiologic preload significantly reduced the VCF deformity (anterior and middle vertebral body heights, segmental and vertebral kyphosis) and returned the compressive load path posteriorly, approaching the prefracture alignment. Application of extension moments also was effective in restoring the prefracture geometric and loading alignment of adjacent segments, but the middle height of the fractured vertebra and vertebral kyphotic deformity were not restored with spinal extension alone.
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Comparative Study
Quantitative analysis of gene expression in a rabbit model of intervertebral disc degeneration by real-time polymerase chain reaction.
Serial analysis of gene expression during the course of intervertebral disc degeneration (IDD) could elucidate valuable insight into pathophysiology and provide a basis for identification of potential targets for the development of novel cellular- and gene-based therapies. However, very few previous studies described the changes in gene expression through the process of IDD using a suitable animal model. ⋯ The gene expression profiles of ECM components and anabolic, catabolic, and anti-catabolic factors demonstrate many characteristics similar to the findings in human disc degeneration and suggest an inability of the intervertebral disc (IVD) to mount an early anabolic response to injury, thereby offering a possible explanation for the disc's lack of reparative capabilities. Catabolic genes are strongly up-regulated both early and late in degeneration, lending strong support to the hypothesis that an anabolic or catabolic imbalance plays a primary role in IDD. According to the resultant patterns, augmenting early production of BMP-2, BMP-7, IGF-1 or TIMP-1 by gene transfer techniques might possibly alter the progressive course of degeneration as seen in the stab model. The next step will be to transfer these therapeutic genes to regulate the biologic processes and ideally alter the progressive course of disc degeneration.