Which landmark should be palpated for the lumbar obliques?

In lumbar oblique positioning for X-ray imaging, L3 is the most relevant spinous process to palpate. This is primarily because when setting up for oblique views of the lumbar spine, radiologists aim to visualize the lumbar zygapophyseal (facet) joints effectively. The L3 spinous process is typically located in a position that allows for accurate angling and placement of the central ray to achieve the desired image of the lumbar facets at the L2-L3 and L3-L4 levels.

The L3 spinous process is central to the lumbar region and provides the best landmark to ensure that the X-ray beam is directed appropriately in accordance with the curvature of the lumbar spine. Positioning at L3 optimally captures the oblique views that are essential for diagnostic purposes.

Having recognized the critical function of the L3 spinous process as a landmark, it becomes clear why this choice is favored for lumbar obliques compared to the other spinous processes, each of which may not provide the same alignment or adequate visualization for diagnostic imaging purposes in this context.