[Anatomical Investigation of the Structures Surrounding the Fourth Lumbar Vertebra Using Computed Tomography]

In the case of ultrasound-guided lum- bar plexus and quadratus lumborum blocks, the mus- cle tissue surrounding the nerve is often used as a marker of the nerves. We examined sectional areas of the muscles surrounding the fourth lumbar vertebrae on computed tomography (CT) images.

Subjects comprised of 102 patients who underwent surgery along with preoperative CT imaging, including transverse process sections of the fourth lumbar vertebra. We measured sectional areas of the musculus erector spinae, quadratus lumborum, and psoas major muscles.

Multiple regression analysis revealed that in males, age and weight were factors influencing sec- tional area for all muscles. However, for females, age only affected -sectional area of the quadratus lumbo- rum.

This investigation clarified that signifi- cant muscle atrophy occurs in elderly individuals. Results indicate that when performing ultrasound- guided deep nerve blocks, it is beneficial to confirm the positional relationship of the nerve with the target muscle before using CT.