Osteonecrosis Intro

Question 1

What is osteonecrosis

Answer 1

Death of bone and marrow due to vascular compromise

Question 2

Osteonecrosis locations (2)

Answer 2

1. Metadiaphyseal (infract)

2. Epiphyseal- AVN

Question 3

etiology of osteonecrosis (and mc)

Answer 3

trauma (mc)
Alcoholism (mc)
Corticosteroids (mc)
Caisson disease

Question 4

Why is prompt tx of fx key in preventing osteonecrosis

Answer 4

Reduces risk
ex. under 12 hr for tx 22% chance, over 12 it is 52%

-femoral neck fx= 15-50% develop AVN

Question 5

What % of pts taking corticosteroids develop osteonecrosis

Answer 5

2% of pts

Question 6

Highest risk indv for taking corticosteroids

Answer 6

5-25% on short duration/high dose

40% renal transplant pts

Question 7

What is the theory of osteonecrosis when taking corticosteroids

Answer 7

Generalized osteoperosis-> subchondral fx-> aseptic necrosis

Question 8

What is caisson disease and how can it lead to osteonecrosis

Answer 8

The ‘bends’ during diving

-nitrogen bubbles come out of solution and act as emoli and result in osetonecrosis

Question 9

Where is AVN typically located and what does it cause

Answer 9

In the epiphysis

• collapse of articular surfave
• leads to pain and altered jt function

Question 10

Where is the most common location of metaphyseal/diaphyseal osteonecrosis

Answer 10

usually in medullary cavity of distal femur

can be cortical infarcs in smaller bones

Question 11

What is one of the main signs of medullary osteonecrosis

Answer 11

Sepiginous rim of sclerosis, centrally located within the bone, with some mixed type lucencies withing
-lesions continuously gets more sclerotic with time

Question 12

How will a medullary infarction look on mr

Answer 12

T2 images will show high signal zone surrounded by serpentine, thin low sig border

Question 13

MC locations of AVN

Answer 13

femoral heads, humeral heads, distal femur, metataraal heads, carpal lunate

Question 14

AVN clinical features

Answer 14

• Vague non specific pain in region
• Pain and decreased ROM progresses over years
• may be muscle atrophy/limp

Question 15

AVN (self limiting or not)

Answer 15

Self limiting- lasts 2-8 years

Question 16

What are the 4 phases of AVN generally

Answer 16

1. Avascular (cell death)
2. Revascularization- new bone deposited (causes sclerosis), new bone easily deformed, old bone reabsobed (causes lucencies)
3. Repair/remodel- Bone deposoion
4. Deformity- Closer the deformed shape to normal the better

Question 17

Stage 1 (avascular)- time frame + what happens

Answer 17

0-12 m- vascular just starts to be compromised

Question 18

First imaging signs in stage 1 (avascualr)

Answer 18

Increased jt space
Metaphyseal osteoperosis
Widened growth plate (in young children)

Question 19

Stage 2 (revascularization)- time frame and signs

Answer 19

6m-4 years

• peripherl sclerotic rim
• ivory type vert look
• Cresent sign**
• flattening of articular surface**
• widdend metaphysis

Question 20

What is the crescent sign and when will you see it

Answer 20

Stage 2 (revascularixation of AVN)

• Lucent line on rim of femoral head indicating a fx in subcortical region
• seen in from leg view

Question 21

Tx if you see a crescent sign

Answer 21

Refer for immediate care: get off weight bearing!

Question 22

What oocurs if you keep weight bearing with crescent sign (stage 2)

Answer 22

Flattening of sup articular margin with step defect seen laterally
-some sclerotic rim around head

Question 23

What will you see in phase 3 (repair) + time frame

Answer 23

1-2 years

• Reconstitution of epiphysis (lay down trabeculation)
• Disapearence of clefts

Question 24

Conservative tx of AVN

Answer 24

Relieve pain
reduce stress/weight bearing
maintain mobility