Final answer:
A lumbar puncture is generally performed between the L3-L4 or L4-L5 levels to avoid injury to the spinal cord and to safely sample CSF, especially when testing for conditions like meningitis.
Step-by-step explanation:
A lumbar puncture is typically performed between the L3-L4 or L4-L5 vertebrae levels in the lower lumbar region of the spinal column. This procedure is designed to safely withdraw cerebrospinal fluid (CSF) for diagnostic testing, most notably for conditions such as meningitis. The CSF resides in the subarachnoid space, which is below the termination of the spinal cord and thus this area is chosen to avoid the risk of injuring central nervous system tissues.
The spinal cord usually terminates at the L1-L2 vertebral level, creating what is known as the "cauda equina," a bundle of nerve roots that resembles a horse's tail. Since the spinal cord itself is not present in the lower lumbar vertebrae, the lumbar puncture can be done safely without the risk of direct injury to the spinal cord. Moreover, the potential for damaging central nervous tissue or encountering blood vessels is greatly reduced, as these are located higher up in the spinal column.