Bone Marrow Concentrate and Stem Cell Injections

Bone marrow concentrate, usually called a stem cell injection, is an orthobiologic made from your own bone marrow. Marrow is drawn from the iliac crest of the pelvis, spun in a centrifuge to concentrate the cells, and placed back into the joint, tendon, ligament or bone. The posts here cover how that is done, what the published research supports, and where claims made elsewhere in this field fall apart. They are written for patients weighing options and for physicians deciding when to refer.

Aspirate is not the same as concentrate

Bone marrow aspirate is the fluid drawn straight out of the marrow space. Bone marrow concentrate is that aspirate after processing, normally a centrifuge step that separates and concentrates the nucleated cells, including the stem and progenitor cells the treatment depends on. Several posts here work through why that step matters, including talking points Don Buford, MD presented as faculty at the 2018 Interventional Orthopedic Foundation meeting, and an answer to the claim that a particular needle removes the need to process marrow at all.

The distinction is not academic. Unprocessed aspirate delivers a lower cell dose in the same volume of fluid, and a clinic that cannot tell you whether your marrow was concentrated is worth questioning.

Technique changes the dose

How the marrow is drawn matters as much as the device. Smaller syringes, smaller volume draws, roughly 6 to 8 cc in a 10 cc syringe, and drawing from multiple depths through a single cortical entry all limit dilution with peripheral blood. Several posts here are head to head tests on the same patient, one needle in each posterior iliac crest, scored by total nucleated cell count and by colony forming units per ml. The numbers are published whether or not they favored the product being tested.

The practice runs an in house lab with five centrifuges and a hematology analyzer, so whole blood, platelet rich plasma and marrow aspirate are quantified for each patient rather than estimated. The PRP hub covers the platelet side of that work, and every injection is placed under ultrasound guidance.

What the evidence supports, and what it does not

The research base is real and uneven, so it is worth being precise. In a practice study of rotator cuff tears treated with a single in office bone marrow concentrate injection, patients reported 80 percent less pain and were 84 percent better by SANE score two years later. A published study of aneurysmal bone cysts reported 80 percent healed after one percutaneous injection of bone marrow concentrate with demineralized bone matrix and platelet rich fibrin, against 74 percent after curettage and bone grafting. For Ficat stage 2 avascular necrosis of the hip there is level 1 data behind replacing avascular marrow with concentrated marrow. A Canadian pilot in 12 patients with advanced knee arthritis is one of the few papers showing a dose response, better outcomes at higher doses of cultured marrow cells, and it reported MRIs unchanged at one year.

Some things do not happen. No published orthopedic study shows that knee X-rays look better after a stem cell injection, and a clinic claiming otherwise deserves hard questions. Results vary, advanced arthritis responds less well than earlier arthritis, and where the literature is mixed these posts say so. The research hub collects the study reviews and the knee hub gathers the knee arthritis material.

The cells have to come from your own body

In the United States a legal orthopedic stem cell procedure uses cells from the patient's own marrow. The FDA regulates adipose derived stromal vascular fraction, amniotic fluid, umbilical cord blood, Wharton's jelly and placental products as biologic drugs when they are used for orthopedic conditions, and independent published testing has found no living stem cells in frozen, shipped birth tissue products. A federal court upheld the FDA injunction against US Stem Cell over adipose SVF, and the New York Attorney General sued a clinic selling the same thing. At a 2020 meeting the director of the FDA's CBER was asked whether a clinician can put adipose SVF or microfat into a knee or a tendon. The answer was no. There are also no meaningful numbers of stem cells in circulating blood, so there are none in PRP either, whatever a podcast may have said. Cells given intravenously are largely trapped in the lung on the first pass. The FDA and safety hub follows these cases.

What the procedure day looks like

The marrow draw and the injection are done in the office under local anesthesia, averaging about 45 minutes, so there is no hospital or surgery center visit. More than one joint can be treated in the same session, and patients here have had both hips and both knees done in one visit. Most people start to notice a change by about 6 weeks and some sooner, though that varies. Bone marrow concentrate is also used with an operation rather than instead of one, placed at a meniscus repair to support healing, or into the bone under a damaged joint surface as well as into the joint.