<Tr> <Th> Drawbacks </Th> <Td> Does not represent all cells </Td> <Td> Slow processing </Td> </Tr> <P> Aspiration does not always represent all cells since some such as lymphoma stick to the trabecula, and would thus be missed by a simple aspiration . </P> <P> Bone marrow aspiration and trephine biopsy are usually performed on the back of the hipbone, or posterior iliac crest . An aspirate can also be obtained from the sternum (breastbone). For the sternal aspirate, the patient lies on their back, with a pillow under the shoulder to raise the chest . A trephine biopsy should never be performed on the sternum, due to the risk of injury to blood vessels, lungs or the heart . Bone marrow aspiration may also be performed on the tibial (shinbone) site in children up to 2 years of age while spinous process aspiration is frequently done in a lumbar puncture position and on the L3 - L4 vertebrae . </P> <P> Anesthesia is used to reduce surface pain at the spot where the needle is inserted . Pain may result from the procedure's insult to the marrow, which cannot be anesthetized, as well as short periods of pain from the anesthetic process itself . The experience is not uniform; different patients report different levels of pain, and some do not report any pain at certain expected points . </P>

Where is bone marrow most commonly aspirated for diagnosis