Is there a difference between a spinal tap and a bone marrow aspiration?

Yes: Spinal tap removes part of the cerebrospinal fluid (the fluid that surrounds the brain and the spinal cord) usually by placing a needle into the spinal column through the back and withdrawal of the fluid. Bone marrow aspiration is done typically by a much larger needle (trocar) which is inserted into the center of the hip bone (rarely the sternum) for the purposes of withdrawing the bone marrow.

SPINAL; BONE MARROW: A spinal tap does not enter bone. In a bone marrow aspiration, the needle is injected directly into the bone to extract the marrow.

YES!!!: You are confused because they are both done on your back but a spinal tap is to obtain the liquid that in in your nervous system around your spine and brain. A bone marrow aspiration is done in the iliac bone to obtain a sample of cells inside the bone cavity where blood cells develop and grow.

Completelt different: Spinal tap is done by putting a needle to the lumbar( lower back area) spinal canal space- to obtain cerebro spinal fluid. Bone marrow aspiration is done on the pelvic bone/hip bone - by putting a needle into the bone- going to the marrow space and aspirate the blood part inside the bone ( i.e. Marrow). The indication, procedure, technique, etc area different. Completely different procedures.