Bone marrow aspiration (BMA) is increasingly being used to harvest stem cells for use in regenerative medicine. The focus of BMA in interventional orthopedics is to maximize the yield of mesenchymal stem cells. The authors present an improved method for BMA that involves fluoroscope or ultrasound guidance combined with anesthesia; in the authors’ experience, it produces the highest possible stem cell yield and is well tolerated by patients. The authors provide a step-by-step guide to the process, along with a discussion of technical and other considerations and quick reference guides for ultrasound- and fluoroscope-guided BMA.
Key points
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Bone marrow aspiration (BMA) is the technique used to harvest stem cells for use in regenerative medicine.
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The use of ultrasound or fluoroscopy guidance represents an advance over traditional palpation-guided techniques. BMA combining anesthesia with guidance can improve patient comfort.
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Newer techniques for BMA allows for higher yields of stem cells.
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Patient preparation, equipment, anesthesia, use of guidance, and medical and other considerations for performing BMA are important.
Introduction
Patients often consider bone marrow aspiration (BMA) to be painful and difficult. Traditionally, BMAs were often performed using palpation-guided techniques that may work well in thin patients but were uncomfortable for most patients and difficult in heavier patients. Additionally, the authors’ experience suggests that this procedure is often not performed in a way that maximizes yield. This article helps physicians understand how to obtain the highest possible stem cell yield while reducing patient discomfort.
Introduction
Patients often consider bone marrow aspiration (BMA) to be painful and difficult. Traditionally, BMAs were often performed using palpation-guided techniques that may work well in thin patients but were uncomfortable for most patients and difficult in heavier patients. Additionally, the authors’ experience suggests that this procedure is often not performed in a way that maximizes yield. This article helps physicians understand how to obtain the highest possible stem cell yield while reducing patient discomfort.
Basic science of stem cells
The International Society for Cellular Therapy definition of a mesenchymal stem cell (MSC) includes a cell line that
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Is plastic adherent
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Expresses CD105, CD73, and CD90 and lacks expression of CD45, CD34, CD14 or CD11b, CD79alpha or CD19, and HLA-DR surface molecules
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Must be capable of trilineage differentiation to osteoblasts, adipocytes, and chondroblasts in vitro
Stem cells are part of the body’s natural healing processes. They are responsible for repair of injured tissues in the body on an ongoing basis. Hence, healing can be enhanced by injecting or surgically placing stem cells into damaged or injured areas.
A recent PubMed search for mesenchymal stem cells reveals more than 40,000 publications. Some studies have shown that MSCs can heal cartilage, bone, ligament, and tendon. Interventional orthopedics is the use of percutaneous techniques under imaging guidance to deliver MSCs and other orthobiologics to promote healing and avoid the need for surgery. There are early clinical data to suggest that, in the future, many orthopedic conditions that previously required surgical intervention may be treatable with guided placement of MSCs.
Later the authors provide an overview of the types of stem cells available in bone marrow ( Fig. 1 ).
Mesenchymal Stem Cells
MSCs, also known as marrow stromal cells or colony-forming fibroblasts, are multipotent adult stem cells that have shown clinical potential as therapeutic agents in regenerative medicine. They are derived from other mesodermal tissues. Experiments in the 1980s and 1990s demonstrated that local environmental factors cause MSCs to differentiate into different cell types. For example, culturing MSCs with ascorbic acid, inorganic phosphate, or dexamethasone causes them to differentiate into osteoblasts, whereas exposure to transforming growth factor beta causes them to differentiate into chondrocytes. More recent research has revealed that MSCs are actually a heterogeneous population of similar cells rather than one distinct cell type.
Hematopoietic Stem Cells
Hematopoietic stem cells (HSCs) are stem cells that are responsible for the production of blood; they are also secondarily involved in muscle repair. In the body they are recruited from the bone marrow when local muscle satellite cells are unable to complete muscle repair.
Endothelial Progenitor Cells
Endothelial progenitor cells are recruited from bone marrow to facilitate vascular homeostasis and neovasculogenesis. This cell type may be useful for reestablishing vascularity in chronically injured musculoskeletal tissues.
Pericytes
Pericytes reside around blood vessels and are recruited from the bone marrow for neovasculogenesis. Some investigators have suggested that they can differentiate into MSCs when injuries occur.
Osteochondral Reticular Cells
These stem cells are concentrated in the metaphysis of long bones but not in the perisinusoidal space. They can differentiate into osteoblasts, chondrocytes, and reticular marrow stromal cells.
Multilineage Differentiating Stress-Enduring Cells
Multilineage differentiating stress-enduring cells can differentiate into endoderm, mesoderm, and ectoderm. They are activated by physical stress and act as a reserve cell source. They are also involved in regenerative homeostasis and tissue repair.
Although bone marrow contains many types of stem and other cells to help orthopedic injuries, the focus of a BMA is to maximize MSC yield.
Basic science of bone marrow and bone marrow aspiration
Drilling into the bone marrow is one of the oldest known medical procedures, with evidence dating back more than 7000 years. The first attempts to obtain an actual bone marrow sample for diagnostic reasons were independently undertaken by Pianese (Italy) and Wolff (Germany) in 1903. The modern Jamshidi needle ( Fig. 2 ), first described in 1971, is a commonly used tool for entering the bone marrow cavity.
Safety, indications, contraindications, medications, and patient preparation
BMA has been performed safely for more than 30 years. A large European Union registry including BMA and bone marrow biopsy shows a serious adverse event rate of 16 in 27,700 procedures. There was one fatality from pulmonary embolism. Pain at the draw site is the most common adverse event.
Indications
BMA is indicated for treatment the following conditions:
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Osteoarthritis
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Tears of ligaments or tendons
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Avascular necrosis
Contraindications
BMA is contraindicated in the following circumstances:
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There is significant anemia; check hematocrit (Hct) if unsure.
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There is local or systemic infection.
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There is active hematologic neoplasm, even if in treatment.
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There is anticoagulant treatment that cannot be stopped for the procedure.
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Patients are unable to be positioned for the procedure.
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There is immune compromise. Patients with immune compromise should not be treated.
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Cancer may be a contraindication. A recent study showed no increased risk of tumor growth when stem cells were used in conjunction with resection of bone cancer and graft placement
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Rheumatoid disease: The authors have treated patients with rheumatoid disease provided they are not in an acute inflammatory phase. The effects of immunosuppressant or biological therapies for rheumatologic diseases on the efficacy of stem cell treatment are unknown.
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Medications: Some medications must be avoided:
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Because of its antiinflammatory and antianabolic effects, prednisone is contraindicated for 4 to 6 weeks before treatment.
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Statins seem to have a very negative effect on stem cell proliferation and should be avoided at least 1 month before to 1 month after treatment.
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Nonsteroidal antiinflammatory medications seem to reduce platelet aggregation and function. In the experience of one of the authors, they may also reduce MSC proliferation. They should be avoided for 1 week before and for 6 weeks after treatment.
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Patient Selection, Body Size, and Positioning
Older patients may have fewer stem cells. They can still be harvested, but a larger volume of bone marrow will be needed to compensate. If properly stimulated, they have been shown to work adequately for tissue repair.
Imaging and BMA can be more challenging in certain individuals:
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Body mass index (BMI): BMI, within limits, is not a predictive factor for knee osteoarthritis outcome but may be more challenging to perform. Larger body size and habitus increase the amount of excess soft tissue to be penetrated; these cases will require longer trocars, which will increase the opportunity for error and pain. The standard trocar is 3.5 in, and for larger patients a 6-in trocar may be required.
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Imaging is more difficult in larger individuals. Fluoroscopic imaging may be beneficial for guidance in these individuals when compared with ultrasound. The ideal position for performing BMA at the posterior superior iliac crest (PSIS) is prone because it allows for the proper imaging of the multiple draw sites located in that area. If patients cannot assume this position easily, it is possible to cannulate the anterior superior iliac crest (ASIS). Such cases are best left for experienced practitioners, as the lateral anterior femoral cutaneous nerve is located here.
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Larger patients and those with respiratory problems may have increased difficulty with respiration in the prone position. The authors recommend that new practitioners gain experience before taking on more challenging cases or refer them to experienced practitioners.
How Much Bone Marrow Aspiration Can Be Safely Drawn?
These guidelines are based on the authors’ experience and patient size:
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Small woman/child (90–105 lb): no more than 50 mL
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Average woman, small man, or a patient with lower Hct (105–150 Hct): 60 to 70 mL
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Larger man/woman (150–250 lb): up to 120 mL
General Bone Marrow Aspiration Volume Requirements for Different Joints
These guidelines are based on the authors’ experience:
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Bilateral knee osteoarthritis (OA): 120 mL
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Unilateral knee OA: 60 to 90 mL
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Medium joint (elbow/transverse tarsal joint axis (TT) ankle): 60 mL
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Small joint/intervertebral disc (IVD): 40 to 60 mL
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Very small joint (finger/foot single): 30 mL one side
Preparation for bone marrow aspiration
Types of Trocars and Differing Techniques
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The bone can be penetrated using either a hand trocar or a commercially available powered driver, such as the one shown in Fig. 8 C. The choice of tool will depend on the patients’ age and bone density and physician preference. Some physicians may prefer a hand trocar; others will prefer a powered driver.
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Bone hardness changes across the lifecycle and becomes softer with age. A greater effort will be required to penetrate the bone of younger individuals and athletes.
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Hand trocars are recommended for older patients (55 years or older) or those with osteoporosis; use of a driver could result in overpenetration.
Maximizing Mesenchymal Stem Cells
Yield
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To maximize MSC yield, the authors recommend targeting the posterior superior iliac spine ( Fig. 3 ) because it contains more MSCs than other bone aspiration sites like the tibia.
Fig. 3
This image shows a patient lying prone on a table, prepped and draped for BMA from the posterior superior iliac spine.
( Courtesy of Terese Winslow LLC, Alexandria, Virginia. 2016; with permission.)
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As shown in Fig. 4 , the ilium has a thick portion and a thin portion. The thickest part of the ilium is the target.
Fig. 4
Cross section of the iliac crest showing thick and thin areas. Penetrating the thin area of the pelvis increases the likelihood of passing through the marrow space. The thick area has a large marrow space with less risk of passing through the marrow-rich area and much higher likelihood of drawing whole marrow.
( Courtesy of Christopher J. Centeno, MD, Broomfield, Colorado.)
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Drawing small volumes (5–15 mL) from many sites increases MSC yield; drawing a large volume (more than 10–15 mL) from a single bone site reduces MSC yield.
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MSCs reside in the subcortical areas; pericytes reside around blood vessels. Penetrating the bone marrow space probably dislodges cortical and perivascular pericytes ( Fig. 5 ).
Fig. 5
There are 2 opportunities to dislodge marrow MSCs.
( Courtesy of Christopher J. Centeno, MD, Broomfield, Colorado.)
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Drawing from more sites maximizes subcortical MSC yield and allows access to pericytes.
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There are other strategies for drawing stem cells. Some practitioners call for going deeper into the marrow and extracting cells at different depths through side port trocars, such as the one shown in Fig. 6 . There are no published data on the efficacy of this method with regard to improving MSC yield.
Fig. 6
BMA needle featuring side ports (only) manufactured by Marrow Cellutions.
( Courtesy of Ranfac Corp, Avon, MA; with permission.)
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Others practitioners suggest using the same entry position and manipulating the trocar to get different areas of the marrow. Again, no data exist on the relative efficacy of this technique over simply penetrating the cortex at multiple sites ( Fig. 7 ).
