European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society
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Stabilizing a lumbar spine with an implant alters the mechanical properties of the bridged region. In order to determine whether this procedure is associated with higher loads in the adjacent segments, seven lumbar cadaver spines were mounted in a spine tester and loaded with pure moments of flexion/extension, left and right lateral bending, and left and right axial rotation. The material studied comprised intact lumbar spines, intact spines with bisegmental internal spinal fixators, and postcorpectomy spines both with a graft and fixators and with fixators alone. ⋯ Highly significant differences in these regions (P<0.01) were far below the interspecimen range. We did not find any case where both intradiscal pressure changes and intersegmental motion showed highly significantly differences in the regions adjacent to the bridged one. Our results suggest that disc degeneration, which is sometimes found at the level directly above and below the fixators, is not caused by mechanical factors.
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Comparative Study
Role of cortical and cancellous bone of the vertebral pedicle in implant fixation.
An experimental study was conducted to determine the role of cancellous and cortical bone of vertebral pedicles in the fixation of pedicular screws. Ten segments of the lumbar spinal column removed from adults at autopsy were used. Direct measurements were made to obtain the total diameter of the pedicles from L1 to L5 plus the diameter of cancellous bone and the diameter of cortical bone. ⋯ The screws used ranged in diameter from 3 to 12.5 mm, with progressive 0.5-mm increments. The analysis of the alterations in pedicle structure was performed by considering total diameter, spongy bone diameter, cortical bone diameter, and diameter of the screw used to produce the structural alteration. The results showed that the screws in general presented fixation mainly in the cancellous bone portion of the vertebral pedicle, whereas a small percentage of cortical bone was used for fixation.
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The Short Form 36 questionnaire (SF-36) measures general health and well-being. Within the last 5 years it has been used increasingly to characterise patients in the medical literature. Relatively few studies have used the SF-36 on patients with chronic low back pain undergoing preoperative evaluation, but results suggest that it may be predictive of surgical outcome. ⋯ The odds ratio (OR) of receiving a nonorganic pain drawing was 22 (95% confidence interval, or CI, 7-65) if the scores on RE and MH were more than 2 standard deviations (SD) below the Danish norm. This is the first study providing evidence that pain drawing ratings are influenced by the psychological scales of the SF-36. The clinical relevance of this observation regarding prediction of outcome after spinal surgery should be assessed in future studies.
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This review presents the history of chemonucleolysis, the techniques, indications, contraindications, and complications. Presenting an historical overview and comparison of success rates with surgical discectomy may provide a fresh understanding of the controversy surrounding chemonucleolysis and establish its efficacy in relation to more invasive treatments. ⋯ In the experience and opinion of the authors, chemonucleolysis remains a viable alternative for patients who have exhausted all conservative means of treatment. Proper patient selection leads to success rates comparable to open discectomy and microdiscectomy.
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Case Reports Comparative Study
Finite element model of the Jefferson fracture: comparison with a cadaver model.
This study tries to explain the reason why the Jefferson fracture is a burst fracture, using two different biomechanical models: a finite element model (FEM) and a cadaver model used to determine strain distribution in C1 during axial static compressive loading. For the FEM model, a three-dimensional model of C1 was obtained from a 29-year-old healthy human, using axial CT scans with intervals of 1.0 mm. The mesh model was composed of 8200 four-noded isoparametric tetrahedrons and 37,400 solid elements. ⋯ The strain values obtained from the two experimental models showed similar trends. The FEM analysis revealed that maximum strain changes occurred where the maximum shear and von Mises stresses were concentrated. The changes in the C1 strain and stress values during static axial loading biomechanically prove that the Jefferson fracture is a burst fracture.