MSK: Bone Marrow

Question 1

At what age should marrow conversion be complete?

Answer 1

By the mid 20s (you are born with all red marrow and this progressively converts to mostly yellow marrow)

Question 2

In what direction does marrow conversion progress?

Answer 2

From peripheral (hands/feet) to central (spine)

Question 3

How does bone marrow conversion progress within a long bone?

Answer 3

• Epiphyses/apophyses (first)
• diaphyses
• distal metaphyses
• Proximal metaphyses (last)

Question 4

Adults have almost all red marrow, except in which locations that also have red marrow?

Answer 4

• Proximal metaphyses of long bones
• Axial skeleton

Note: Red marrow can also be found in the humeral and femoral heads as a normal variant.

Question 5

As trabecular bone decreases with osteoporosis, it is replaced with…

Answer 5

Yellow marrow

Question 6

What is the best sequence to evaluate red/yellow marrow?

Answer 6

T1 (yellow marrow is bright and red marrow is nearly isointense to muscle)

Question 7

How can you tell if red marrow is darker than it should be?

Answer 7

Red marrow should never be darker than muscle (or a normal intervertebral disc) on T1

Note: If it is darker, be suspicious of replacement with leukemic cells.

Question 8

When might red marrow increase in an adult?

Answer 8

If there is a need for more hematopoiesis

Note: Reconversion occurs in the exact reverse order as marrow conversion.

Question 9

What can cause marrow to turn yellow in the spine?

Answer 9

Stress/degenerative change

Question 10

What is the first part of bone to convert to yellow marrow?

Answer 10

Epiphyses (these convert to yellow marrow almost immediately after ossification)

Question 11

Distal femoral red marrow is commonly seen in what pts?

Answer 11

Teenagers and menstruating women

Question 12

Answer 12

Lucent metaphyseal bands in a child, suspicious for leukemia

Question 13

Answer 13

Diffuse T1 marrow signal loss, concerning for infiltration (e.g. leukemia)

Note: Red marrow is still 40% fat and should be brighter than intervertebral discs and muscle on T1.

Question 14

Differential for speckled bone marrow deposits?

Answer 14

• Multiple myeloma
• Waldenstroms macroglobulinemia (subtype of B cell lymphoma)

Question 15

Destructive mass in the bone of a leukemia pt…

Answer 15

Think chroma (granulocytic sarcoma)

Question 16

Pt with history of leukemia

Answer 16

Think chloroma (AKA granulocytic sarcoma)