Osteoporosis Diagnose

How do We Diagnose Osteoporosis?
Osteoporosis is diagnosed with the help of densitometric techniques. At present various types of bone densitometers (discussed below) are used to diagnose it. The density of bone is classified as normal, osteopenic(decreased calcification of bones) or osteoporotic (very thin bones).

X-Ray
Until the advent of bone densitometric studies, X-rays were commonly used to diagnose osteoporosis. In the spine, marked thinning of inner ( cancellous) bone can be seen. There is accentuation of the cortical ( Outer part) of bone. In severe cases, this thinning of inner bone with outer bone remaining of normal thickness, produces the so-called picture – framing effect of the affected vertebra. ( In a picture frame, the frame is seen but inside it is empty space). In marked osteoporosis, there can even be fragmentation of the vertebrae.
However, X=rays are not that reliable in detecting osteoporosis due to the following limitations :

· It cannot detect early osteoporosis. At least 30 per cent of the skeletal calcium must be lost before osteoporosis becomes detectable on conventional X-ray.
· X-ray image quality also varies according to the type of machine, the expertise of the technician, etc., which is not reliable for comparative analysis. 

Bone Densitometry
Individuals at increased fracture risk can be assessed with BMD ( bone mineral density) testing, which measure the demineralization of the bones. This evaluation can be done by DEXA (Dual energy X-ray absorbitometry) or by ultrasonography. 
DEXA is the gold standard in BMD studies. BMD can be measured at the calcaneus ( heel bone) or the proximal femur (thigh bone). However, the heel DEXA is performed more frequently as it is cheaper. BMD can also be measured on a mass scale by sonography, but it is not as accurate as DEXA.

Uses of BMD
· This permits accurate and precise measurement of bone mass at different skeletal sites. 
· This method helps in predicting future fractures in vulnerable groups. This capability is important for early identification of high – risk individuals in the course of their disease to ensure timely treatment in order to slow down the rate of bone loss. 
· It is also useful in diagnosing osteoporosis among patients who have already begun to develop fractures or who have other disorders that might be associated with excessive bone loss. 
· Another role is in assessing rates of bone loss. 
· Lastly, it can be used in following up the course of the disease or in assessing the results of treatment.

When should a person have a BMD measured?
· All post-menopausal women should have their BMD measured if they suffer a fracture. 
· If there is a family history of osteoporosis ( especially the mother or nearest relatives), particularly with a fracture. 
· If a persons is a smoker. 
· If a person is markedly underweight. 
· If the person is taking a drug that is known to cause osteoporosis. 
· If there is a disease that is known to lead to bone loss. 

A person with established osteoporosis should repeat the BMD testing every year for at least two years.

What is a T-score: Results of BMD are interpreted in the form of a T-score. It compares the bone density of the person with the density of a 25-year-old person. On the basis of T-score the condition can be classified as 
Osteopenia = score between –1.5 to –2.5 (patient has not yet developed osteoporosis)

Osteoporosis = score less than –2.5


Thin bone
Figure 3 BMD picture showing areas of thinning of bone