World Health Organization. Assessment for fracture risk and its application to screening for postmenopausal osteoporosis.

Normal T score: -1.0 and above

Osteopenia: -1.0 to -2.5

Osteoporosis: -2.5 and below

Primary Osteoporosis

vs.

Secondary Osteoporosis

Primary (type I)is associated with the process of normal aging. Estrogen and progesterone are two hormones that play important roles in regulating the rate at which bone is lost.

Secondary (type II) can be caused by certain medical conditions and medications that can disrupt bone reformation.

Smoking

Calcium Intake

Estrogen

Sedentary Lifestyle

Eating Disorders

Excessive Alcohol

Corticosteroids

SSRI Inhibitors, Methotrexate, Anti-seizure med, Acid blocking drugs

Structural support and protection

Storage of essential minerals

Production of blood cells

Storage of chemical energy

compact bone

much denser

found primary is found in the shaft of long bones and forms the outer shell around cancellous bone at the end of joints and the vertebrae

known as cancellous or spongy bone

much more porous

found in the end of long bones,in vertebrae and in flat bones like the pelvis  

Bone Remodeling

bone formation and bone resorption and consists of five phases:

1. activation: preosteoclasts are stimulated and differentiate under the influence of cytokines and growth factors into mature active osteoclasts
2. resorption: osteoclasts digest mineral matrix (old bone)
3. reversal: end of resorption
4. formation: osteoblasts synthesize new bone matrix
5. quiescence: osteoblasts become resting bone lining cells on the newly formed bone surface

Bone Health:

 Good Nutrition

Dairy products are high in calcium

Vitamin D helps your body use calcium

Fish contain Ca and Vit D, Fortified foods

Fruits and vegetables contain necessary vitamins.

Meat and other high protein foods

Poor Nutrition & Bone Loss

salt (sodium) causes your body to lose calcium and can lead to bone loss.

Spinach and other foods with oxalates.

Wheat bran contains high levels of phytates which can prevent your body from absorbing calcium.

Alcohol, Coffee, tea and soft drinks.

Weight-bearing exercises

Muscle-Strengthening Exercises

Non-Impact Exercises

Non-Weight-Bearing, Non-Impact Exercises

BMD Testing Method:

Central Densitometry & Devices

Measures spine, ribs,sternum, pelvis, proximal femur.

Dual-Energy x-ray abdorptiometry (DXA)

Quantitative computed tomography (QCT)

"Gold Standard", most known, excellent reproducibility,low dose, used in most used in most epidemiologic studies, well known how BMD relates to fracture risk, used in most trial studies

BMD Testing Method:

 Peripheral Densitometry & Devices

Measures wrist, heel finger, etc.

Peripheral DXA (pDXA)

Single X-ray Absorptiometry (SXA)

Peripheral QCT (pQCT)

Qualitative Ultrasound (QUS)

Radiographic Absorptiometry (RA)

 (DXA)

Dual-Energy x-ray abdorptiometry

Why dual energy?

At low energy, bone attenuation is greater than soft tissue attenuation. At high energy, bone attenuation is similar to soft tissue attenuation.

BMD Testing Methods:

Single X-ray Absorptiometry (SXA)

Measure heel or forearm

Require water bath for soft tissue equalization

Are being replaced by DXA systems

Compared to central devices, they are smaller, portable, lower dose, shorter scan time, easier to operate, less expensive

BMD Testing Methods:

Quantitative Ultrasound (QUS) 

Greater technologic diversity than DXA

No radiation

Does not measure BMD

Can only be used peripherally

Measure at heel, finger, tibia, etc.

Basic Statistical Concepts:

Mean

Average

Add all the data values and divide by the number of values

Basic Statistical Concepts:

Standard Deviation (SD)

Measurement of the spread of the data values around the mean

The wider the spread, the larger the SD

For 2 data sets, the mean can be the same, but SD different.

For DXA, smaller SD is better

Basic Statistical Concepts:

Percent coefficient of variation

(%CV)

(%CV) = (SD/mean) x 100

Allows  for comparison of variability in different data sets

Used to check daily QC plot

Smaller %CV means there is less variability in data, which is better for DXA results.

Used to express precision

Patient Results:

BMD formula

BMD = BMC/area

If BMC and Area both move up or down, they cancel their effect on BMD and BMD remains constant.

Z - Score

Comparison of patients current BMD to BMD of same age group.

 The age matched z-score indicates how much the patient deviates from the mean Age Matched Values.

Should be population & ethnicity specific

Z-Score=(patient BMD-Age Matched Ref. BMD)/Age Matched Ref. SD

T - Score

Comparison of patient's current BMD to BMD at peak bone mass

used primarily for the diagnosis of osteoporosis.

For Reference Database, use a uniform Caucasian.

T-score=(patient BMD-Peak Ref. BMD)/Peak Ref. SD