Spine
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An in vitro biomechanical study of adjacent segment motion (at L3-L4 and L5-S1) after a simulated lumbar interbody fusion of L4-L5 in different sagittal alignments was carried out. ⋯ Hypolordotic alignment at L4-L5 caused the greatest amount of flexion-extension motion at L3-L4, and the differences were statistically significant in comparison with intact specimen, in situ fixation, and hyperlordotic fixation. Hyperlordotic alignment at L4-L5 caused the greatest amount of flexion-extension motion at L5-S1, and the difference was statistically significant in comparison with intact specimen but not in situ fixation or hypolordotic fixation.
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To assess the biomechanical effects of unipedicular vertebroplasty on nonfractured vertebrae. ⋯ The introduction of 20% bone cement by volume results in a significant increase in the compressive strength of intact lumbar vertebrae, however upper thoracic vertebrae do not demonstrate a similar strength improvement. There was no difference in the stiffness of the vertebrae injected with cement regardless of location. Bone mineral density (BMD) may play a role in the magnitude of the strength increase, with lower BMD specimens realizing a relatively greater strength improvement. Cement leakage was frequently noted with 20% cement injection, especially in the specimens with higher BMD. The location of the cement did not appear to have an effect on the loading behavior of the bone but should be controlled to minimize the chance of cement escaping into the spinal canal.
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This is a case report of a young patient who experienced an acute epidural compression of cauda equina revealing Stage IV Hodgkin's disease. ⋯ Although a rare situation, Hodgkin's disease may involve the spinal epidural space at presentation. The management is complex, but surgery provides the most rapid means of diagnosis and neurologic tissue decompression in severely affected patients.
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Pedicle screw fixation alone for sequential spinal instabilities was biomechanically compared with pedicle screw fixation using interbody cages. ⋯ For spinal instability with preserved anterior load sharing, pedicle screw fixation alone is biomechanically adequate, and interbody cages should not be used because they further increase segmental motion at the adjacent segment. However, PS alone provides insufficient stability and high implant strain in case of damaged anterior column. In such cases, additional interbody cages significantly increase construct stiffness and decrease hardware strain. However, they increase ROM at the adjacent segment as well.
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A biomechanical cadaveric study of thoracic and lumbar vertebrae with simulated metastases quantifying intravertebral pressures during transpedicular vertebroplasty. ⋯ Percutaneous vertebroplasty produces higher intravertebral pressures in vertebrae containing a simulated lytic metastasis than in intact vertebrae. Pressures generated in the tumor specimens are sufficiently elevated to cause embolic phenomena.