Jacoby line
A line connecting the highest points of the left and right iliac crests. The horizontal plane containing this line is the supracristal plane. Equivalent to the height of the spinous process of the fourth lumbar vertebra. In Japanese radiographic studies, the Jacoby line passes through the sites shown in the table below:

  Male (%) Female (%)
Body of lumber vertebra IV 28.9 11.3
Intervertebraldisc of lumber vertebra IV & V 40.9 30.5
Body of lumber vertebra V 30.3 58.2

In adults, the lower end of the spinal cord is at the second lumbar vertebra (L2). Therefore, the Jacoby line is used as an indicator when performing a lumbar puncture between the third and fourth lumbar vertebrae to avoid damaging the spinal cord.