FM Radiology Case - Osteoporosis

Question 1

Osteoporosis is characterized by a decrease in ___, with preservation of ___.

Answer 1

Bone matrix; mineralization

Question 2

List 3 risk factors for osteoporosis.

Answer 2

1. Age
2. Long term use of steroids
3. Smoking

Question 3

When should you suspect osteoporosis?

Answer 3

1. Loss of height with aging
2. Kyphosis with aging (asymptomatic)
3. Compression fractures of vertebra
4. Any fracture after age 40
5. Adult weighing less than 125 lbs
6. Fracture of wrist, spine, or hip in a first-degree relative after age 50

Question 4

List the 2 commonly used types of peripheral bone density measurements.

Answer 4

1. Dual-energy X-ray Absorptiometry (DXA)

2. Quantitative CT (QCT)

Question 5

What is the gold standard for measuring peripheral bone density?

Answer 5

DXA scan

Question 6

Compare the parts of the body studied with DXA vs. QCT.

Answer 6

DXA - posteroanterior lumbar spine and proximal femur

QCT - lumbar spine

Question 7

How does a DXA scan work?

Answer 7

X-rays with two energy peaks are produced, allowing different absorption of radiation by bone and soft tissue, from which bone mineral density (BMD) is calculated

Question 8

What is unique about a QCT?

Answer 8

Measures trabecular bone density

Question 9

QCT is probably the most ___ test in measuring changes in bone density. However, it is not as precise as DXA and is not as widely used - why?

Answer 9

Sensitive; higher radiation dose

Question 10

What bone density measurement site correlates best with clinically important fractures?

Answer 10

The hip is the best site for predicting clinically important fractures.

Question 11

What is a T-score?

Answer 11

The number of standard deviations the bone mineral density measurement is above or below the young (30 y/o) normal mean bone mineral density

Question 12

T-score = ?

Answer 12

(Patient’s BMD - Young adult mean BMD)/Standard deviation of young adult BMD

Question 13

What is a Z-score?

Answer 13

The number of standard deviations the measurement is above or below the age-matched mean bone mineral density

Question 14

Z-score = ?

Answer 14

(Patient’s BMD - Peer age group mean BMD)/Standard deviation of peer age group BMD

Question 15

T-score is the standard used to determine the risk for ___.

Answer 15

Fractures

Question 16

T-score normal range?

Answer 16

-1 to +1

Question 17

T-score range for osteopenia?

Answer 17

-1 to -2.5

Question 18

T-score range for osteoporosis?

Answer 18

-2.5

Question 19

Which site is used in clinical decisions?

Answer 19

Hip

Question 20

If the T-score is the standard used to determine the risk for fractures, what is the Z-score used for?

Answer 20

Determining whether the BMD is less than the age-related bone loss - this would call for investigation of causes of osteoporosis unrealted to age

Question 21

What is the clinical recommendation regarding osteoporosis screening?

Answer 21

For women over 50 and under 65, you need at least one risk factor to recommend DXA scan.

Question 22

What factors contribute to the estimate of the annual cost of screening all potential subjects in the US?

Answer 22

1. # of F over 65
2. # of F between 50-65 with risk factor
3. Cost of DXA

Question 23

How do you justify the cost of annual screening for osteoporosis?

Answer 23

Prevention of morbidity due to vertebral fractures