Mod 4-2 Ischemic (Avascular) Necrosis

Question 1

What is Avascular Necrosis?

Answer 1

Loss of blood supply to the bone

Question 2

What will the amount of necrosis depend upon?

Answer 2

The mechanism of compromise (what causes the decrease in blood flow and how big is the vascular area that is involved).

Question 3

List causes of osteonecrosis

Answer 3

• Infection
• Trauma
• Autoimmune disorders
• Long-term use of steroids (35%)
• Cushing’s disease
• Hemolytic anemia (sickle cell)
• Chronic alcoholism
• Chronic pancreatitis
• Gaucher’s disease
• Radiation Therapy
• Caisson disease (from underwater diving, bends)

Question 4

What are the most common sites of osteonecrosis?

Answer 4

• Femoral and humeral heads
• Talus body
• Carpal scaphoid

Question 5

How many phases are there of ischemic necrosis (osteonecrosis)?

Answer 5

4 phases

Question 6

List the 4 phases of osteonecrosis

Answer 6

1. Disruption of the blood supply to the area
2. Bone fragmentation and resorption
3. Proliferation of granulation tissue and revascularization of the affected area (blood flow re-established and healing begins)
4. Production of new bone

Question 7

The process of avascular necrosis is said to be ____ ______.

Answer 7

self limiting

Question 8

Why is osteonecrosis considered to be self-limiting?

Answer 8

Because as part of the disease pattern teh bone will revascularize itself and begin its own repair.

Question 9

What stage will the dying bone appear denser than the surrounding bone in osteonecrosis?

Answer 9

The necrotic stage

Question 10

What is a symptom of osteonecrosis?

Answer 10

Sudden pain however some are asymptomatic.

Question 11

What will most with osteonecrosis develop later?

Answer 11

MEchanical pain as the femoral head (or other involved joint) collapses. Induced by standing, walking, moving, coughing or other mechanical stress.

*Patients with advanced disease have pain at rest

Question 12

What may be the first sign of osteonecrosis in children?

Answer 12

Limping when teh hip is involved as the femoral head collapses

*THIS MAY LEAD TO OSTEOARTHRITIS

Question 13

What is the first sign that the bone is fragmenting in osteonecrosis?

Answer 13

A radiolucent band representing a fracture.

*Crescent sign

Question 14

In osteonecrosis there will be a pattern of lysis (________) followed by a period of ________ (new bone production)

Answer 14

disintegration; sclerosis

Question 15

What type of pattern happens as a result of lysis and sclerosis?

Answer 15

Mottled pattern of bone at the disease site.

Question 16

What does the crescent sign represent in osteonecrosis?

Answer 16

A fracture in the collapsing bone

Question 17

What modalities are more useful and sensitive methods for following the progression of osteonecrosis?

Answer 17

MRI and Nuc Med

Question 18

What is recommended for technique on patients with osteonecrosis?

Answer 18

Radiographs of varying techniques to see all involved bones. One with normal technique and one made at a higher kVp to penetrate the sclerotic areas.

Question 19

What is the most common site of ischemic necrosis?

Answer 19

The femoral head