Spine
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Although the extent of injury after cervical spine fracture can be visualized by imaging, the deformations that occur in the spinal canal during injury are unknown. ⋯ Two potential spinal cord injury-causing mechanisms in axial bursting injuries of the cervical spine are occlusion and shortening of the canal. Post-injury radiographic measurements significantly underestimate the actual transient injury that occurs during impact.
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Three-dimensional reconstructions of MRI scans measured volume, height, and diameter of intervertebral discs. These measurements were made in vivo. ⋯ The mean simulated diurnal volume decrease in the lower three lumbar discs is 16.2%. Most of the diurnal loss in disc height is due to volume loss. The effect of radial bulging is minimal.
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We measured the cross-sectional area of the intervertebral discs of normal volunteers after an overnight rest; before, during, and after 5 or 17 weeks of bed rest; and before and after 8 days of weightlessness. ⋯ Significant adaptive changes in the intervertebral discs can be expected during weightlessness. These changes, which are rapidly reversible after short-duration flights, may be an important factor during and after long-duration missions.
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A prospective cross-sectional analytic approach was taken. ⋯ In patients with chronic low back pain, the combination of discogenic pain and zygapophyseal joint pain is uncommon.
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Anatomical study of L4 nerve branch, L5 nerve root, and bony stock in the sacroiliac region was performed in cadaveric specimens to provide anatomical references for anterior fixation of the sacroiliac joint. At 1 cm intervals along the sacro-iliac joint, the distance to the lateral border of the L4 nerve branch (to the lumbosacral trunk) and the L5 nerve root was measured. Computed tomography scans and cadaveric sectioning of the sacro-iliac region were performed to evaluate the bony stock available for fixation and the optimal screw direction to prevent neurologic damage. ⋯ Four centimeters cephalad to the pelvic brim, the AP dimension of Sl complex was decreased. Screws that were 1 cm medial to the Sl joint and directed posteriorly and parallel to the joint did not endanger neurologic structures. At four centimeters above the pelvic brim, there is less danger of neurologic injury; however, a decrease in sacral bony stock may affect fixation.