Bone Marrow Biopsy and Aspirate

Summary of the Procedure:

Landmarks:

Humeral head (most commonly used):

• Flex the shoulder joint and identify the acromion of the scapula and greater tubercle of the humerus.  Palpate a flat depression on the craniolateral aspect of the greater tubercle.  This is the landmark for placing the needle, which is advanced caudoventrally at a 45-60^o angle.

Wing of ilium:

• Identify both iliac crests and lumbosacral spinous processes.
• Palpate caudally along the iliac crest.  The preferred site for needle placement is at the last palpable part of the crest, since the ilium is thicker there.  The needle is directed dorsoventrally perpendicular to the iliac crest.  A core biopsy may also be obtained by directing the needle across this area of the ilium.  To minimize the risk of vertebral body penetration, the coring needle may also be directly in a ventrolateral direction across the ilium beginning on its dorsomedial surface.
• This site is challenging to obtain a biopsy from, compared to the humerus.

Trochanteric fossa:

• Identifying the trochanter major of the femur and ischium (rotating the femur outwards will displace your thumb when placed between these two landmarks).  The needle is inserted just medial to the trochanter major and is advanced parallel to the femur along the trochanter major into the trochanteric fossa.

Details of the Procedure:

• Surgically prepare a 4-6 cm 2 area over the biopsy site.
• Inject 0.5 – 1.0 mL lidocaine subcutaneously and use an additional 0.5 – 1.0 mL to infiltrate the muscle and periosteum. A fair amount of resistance is encountered when injecting the periosteum.
• Make a stab incision with the scalpel blade.
• Draw up 0.3 mL of EDTA into the syringe. Remove the aspiration needle stylette and prime the needle with EDTA, leaving 0.1 mL remaining in the syringe.  Replace the stylette into the needle.
• Hold the needle from the top handle and insert it into the bone using a back and forth rotating action. The goal is to initially place the tip of the coring sheath just below the cortex (as illustrated).  When the needle is firmly imbedded, remove the stylette.
• Using moderate pressure, rotate the needle back and forth through the marrow cavity (alternatively rotate it 25 times in both directions) until the opposite cortex is reached. The opposite cortex has been reached when the needle can no longer advance (it cannot penetrate the cortex easily without the stylette), or when the animal reacts more (from irritating the endosteum).  (Note: this procedure is often less painful than aspiration.)
• Carefully withdraw the needle several mm.  Some needles (e.g., disposable Jamshidi-type needles like in the video below) have either a sample capture device that is activated once the marrow sample is obtained. This holds the sample safely in the needle when the needle is being withdrawn from the bone.
• Carefully direct the specimen retrieval probe into the bottom of the needle to push the core out the top. Careful as the needle is sharp.  The core may be rolled on a glass slide for cytology, and then placed into formalin for histology.
• Apply pressure to the site for a few minutes to minimize hematoma formation. A single suture (e.g., cruciate suture) may be needed to close the incision site.
• The needle can be advanced into the bone again, in the same manner as before, to obtain a bone marrow aspirate. Once the stylet is removed, a syringe is attached to the needle, and forceful aspirations are performed to retrieve marrow fluid. This is performed after the biopsy, so that the aspiration does not compromise the architecture of your biopsy sample.
• Cytology should be prepared by placing one drop of bone marrow fluid at the top of the slide, holding the slide at a 90-degree angle to allow the excess blood to run off prior to making a smear. The slides should then be waved back and forth (or a fan used) to dry the sample (leads to better quality of samples versus letting dry on their own).

Example of a Bone Marrow Biopsy and Aspirate:

Alternative Technique – Sternal Bone Marrow Aspirate:

A sternal bone marrow aspirate can be performed in a lightly sedated dog. The advantage of this procedure is the avoidance of general anesthesia. The disadvantage of this procedure is the lack of core bone marrow tissue for histopathology. Bone marrow aspirates are sometimes used when there is a high suspicion of leukemias or other round cell tumour, as this is often sufficient to make a diagnosis of round cell neoplasia. Aspirate is also sometimes used when the patient is not a good candidate for anaesthesia, if the clinician and client understand the potential limitations of this technique.

• For this technique, a 1-inch, 20 to 23-gauge needle OR a spinal needle is used.
• Place the dog in sternal recumbency, and palpate the point of the manubrium.
• Light sedation is administered – do not sedate the dog too much as you want the dog awake enough to maintain sternal recumbency easily. Local lidocaine infusion can be performed.
• Clip and surgically prepare a 4-6 cm 2 area over the aspirate site. Palpate the tip of the manubrium with one gloved hand, and hold the syringe/needle at the hub of the needle.
• Introduce the needle into the skin & subcutaneous tissues to the point of the manubrium bone.
• At this point, the needle is advanced parallel to the manubrium and into the bone while making small rotating motions.
• Once the needle is firmly seated into the bone,  aspiration with the syringe commences.
  • If a spinal needle is being used, remove the stylet once the needle and attach the syringe.
• Remember that aspiration may be painful and the lightly sedated dog may react at this time.  Once there is a small amount of marrow collected in the syringe, stop aspiration and remove the needle from the dog. Apply light pressure to the site for 2 minutes to minimize hematoma formation.