Final answer:
The proper needle placement for a lumbar myelogram is between the 4th and 5th lumbar vertebrae, as this area is a relatively safe location due to the spinal cord not extending beyond the upper lumbar vertebrae.
Step-by-step explanation:
The proper needle placement for a lumbar myelogram is between the 4th and 5th lumbar vertebrae. A lumbar puncture is a medical procedure used to sample the cerebrospinal fluid (CSF), and it is performed in the lower lumbar area of the vertebral column to avoid the risk of damaging CNS tissue. This is because the spinal cord ends at the upper lumbar vertebrae, which makes the space between the 4th and 5th lumbar vertebrae a relatively safe location for the procedure. The lumbar vertebrae are numbered L1-L5, and the lumbar puncture targets the area low enough to prevent injury to the spinal cord, specifically where there is a larger volume of CSF.