Bone marrow is removed by inserting a hollow needle through the skin and into bone, most often the back of the hip. The procedure takes different forms depending on why it’s being done: a quick bedside aspiration to draw out liquid marrow, a biopsy to capture a small core of solid marrow tissue, or a larger surgical harvest to collect stem cells for transplant. All three use the same basic principle of penetrating the outer shell of bone to reach the soft, blood-producing tissue inside.
Where the Marrow Comes From
Not all bones contain usable marrow. Long bones like those in your arms and legs are mostly filled with fatty yellow marrow. The marrow doctors need, the red marrow that actively produces blood cells, is concentrated in flat bones and certain thick, spongy regions. The posterior superior iliac spine, a bony ridge at the back of your pelvis, is the preferred collection site. It has the thickest bone of any spot on the iliac crest, provides the highest yield of stem cells, and carries a lower risk of nerve or blood vessel injury than other locations. The back of the pelvis also simply holds more marrow than the front, making it the go-to site for both diagnostic sampling and donation harvests.
In children or in specific clinical situations, marrow is occasionally drawn from the breastbone (sternum) or the shinbone (tibia), but pelvic collection remains the standard for adults.
Aspiration: Drawing Liquid Marrow
A bone marrow aspiration pulls a small amount of liquid marrow out through a syringe. You lie face down or on your side, and the skin over the back of your hip is cleaned and numbed with a local anesthetic. The doctor then pushes a specialized hollow needle through the skin, through a thin layer of tissue, and into the outer shell of the bone. Once the needle tip reaches the marrow cavity, a syringe is attached and a small volume, typically just 1 to 2 milliliters, is drawn out. Pulling more than that risks diluting the sample with regular blood, which makes lab results less accurate.
The moment of aspiration is the part most people remember. Even with good numbing, you’ll likely feel a brief, sharp pulling sensation as the marrow is sucked into the syringe. It’s often described as a deep ache or tugging that lasts only a few seconds. The entire procedure, from needle insertion to removal, usually takes under 10 minutes.
Biopsy: Capturing a Solid Core
A biopsy is often done at the same time as an aspiration, using the same entry point. Instead of drawing liquid, the goal is to extract a tiny cylinder of solid bone and marrow tissue, usually about the width of a pencil lead and a centimeter or two long. This intact core lets pathologists examine the marrow’s structure, cellularity, and any abnormal cells in a way that liquid samples can’t show.
The needle used for this is a clever piece of engineering called a Jamshidi needle. It’s a long, hollow tube with a sharp, tapered cutting tip and a removable inner rod (stylet). The tapered interior diameter is the key design feature: it widens as you move away from the tip, so the core of tissue slides freely into the needle without being crushed. Once the core is captured, a thin guidewire is threaded through the back end to push the sample out the wide end, avoiding compression against the sharp tip. Modern versions are disposable, but the fundamental design has remained the same for decades because it works so well.
During the biopsy portion, you’ll feel more pressure and a twisting sensation as the needle is rotated to cut through bone. It’s uncomfortable but typically brief.
Surgical Harvest for Transplant
When marrow is being collected for a stem cell transplant, the process is more involved. This is a surgical procedure performed in an operating room under general anesthesia, so donors are completely asleep and feel nothing during it. Needles are inserted through the skin into the back of the pelvic bone in multiple spots, and marrow is drawn out repeatedly until enough has been collected. The process typically takes 1 to 2 hours.
The volume removed is much larger than a diagnostic sample, often several hundred milliliters, but your body replaces the lost marrow over the following weeks. Donors generally feel sore at the collection sites for a few days to a couple of weeks afterward, similar to a deep bruise.
Pain Management Options
For diagnostic aspirations and biopsies, you have a few choices. The simplest approach is local anesthesia alone, where a numbing agent is injected into the skin and the tissue down to the bone surface. This blocks most of the pain, though you’ll still feel that characteristic pulling sensation during aspiration. Many people opt to add light sedation on top of the local anesthetic, delivered through an IV, which takes the edge off anxiety and discomfort. If you’re especially anxious or pain-sensitive, deeper sedation is available so you’re partially or fully unaware during the procedure.
For surgical harvests, general anesthesia is standard.
What Happens to the Sample
Once marrow leaves your body, handling it correctly is time-sensitive. The liquid aspirate is immediately placed into tubes coated with an anticoagulant to prevent clotting, which is one of the most common reasons samples become unusable. Technicians invert each tube right away to mix the anticoagulant thoroughly. A portion of the aspirate may be placed onto a small glass dish for immediate examination under a microscope.
Samples are best kept at room temperature rather than refrigerated, as this preserves cell viability. For diagnostic testing, the marrow should ideally be processed within 24 hours of collection, though samples can remain usable for up to 72 hours at room temperature if necessary. Solid biopsy cores are preserved separately, typically in a fixative solution, for structural analysis by a pathologist.
Risks and Complications
Bone marrow extraction is a low-risk procedure. In a study of 285 marrow harvest procedures, only about 5% resulted in any meaningful complication at the collection site. The most common issues were small hematomas (localized bruising under the skin), temporary numbness near the site (which resolved within three months in all cases), and minor skin irritation or superficial infection that cleared up within a month with basic treatment. No serious complications like deep infection or pelvic fracture occurred.
The posterior iliac crest is chosen specifically because the anatomy there makes serious injury unlikely. The bone is thick, the major nerves and blood vessels are a safe distance away, and the area tolerates repeated needle passes well. Bleeding at the site is controlled with simple pressure and a bandage after the procedure.
Recovery After the Procedure
For a diagnostic aspiration or biopsy, recovery is quick. You’ll have a pressure bandage on the site, and soreness at the collection area is normal for a few days. Most people return to their usual activities within 24 hours, though you may want to avoid heavy lifting or vigorous exercise for a day or two. Over-the-counter pain relievers are usually enough to manage any discomfort.
Recovery from a surgical donation harvest takes longer. Soreness and stiffness around the hip area can last one to two weeks, and some donors report fatigue as their body works to regenerate the collected marrow. Most donors feel back to normal within two to four weeks.