Establishing intercrestal line by posture:--a radiographic evaluation.

In this study, we examined the position of intercrestal line that is called Jacoby's line at heights of the vertebral body and spinous process in different positions of the lumbar spine using radiographs of 100 subjects. At the height of the spinous process, Jacoby's line was most often observed in the extension position in L4 spinous process middle 1/3 region in males and in L4-5 interspinous region in females. In the neutral position, it was in L4 spinous process middle 1/3 region in males and in L4-5 interspinous region in females. And that in the flexion position, it was in L4-5 interspinous region in both males and females. At the height of the vertebral body, Jacoby's line was most often observed in the extension position in L4-5 intervertebral region in males and in L5 vertebral body upper 1/3 region in females. In the neutral position, it was in L4 vertebral body lower 1/3 region in males and in L5 vertebral body upper 1/3 region in females. In the flexion position, it was in L5 vertebral body upper 1/3 region in males and in L5 vertebral body upper 1/3 region or L4 vertebral body lower 1/3 region in females. There was no gender difference in the most often observed position of Jacoby's line at the height of the spinous process in the flexion position. The position of Jacoby's line was found to vary in different positions of the lumbar spine. Positioning Jacoby's line in the neutral lumbar spine from the body surface, as conventionally proposed, was not always accurate, and it was considered practical to establish Jacoby's line using the spinous process in the flexion of the lumbar spine as the standard. When Jacoby's line is established by this method, it is considered to be positioned between L4-5 spinous processes middle 1/3 regions. In subarachnoid puncture in elderly patients, the puncture may be performed at a higher position in relation to the spinal cord because of spinal degeneration. Therefore, it is important to perform subarachnoid puncture in elderly patients at a site lower than the established Jacoby's line.