Wednesday, August 14, 2013

Bone Mineral Density

 A common myth among patients is that all bone related or orthopaedic problems are related to a lack of calcium. Daily, I see patients who are taking calcium supplements on their own accord. People especially women feel that they need to take calcium beyond a certain age, or taking calcium will prevent orthopaedic problems in the future. Usually it is a friend or family member that has scared a person into taking calcium supplements. 

It is wrong to attribute all bone problems to calcium. Often the source of musculoskeletal pain is a joint! There are many joints in the body. Everyone is familiar with the large joints like the hip or knee and small joints like the ones found in the hand and foot. There are also lesser known joints like the facet joints found in the spine (neck and back). Inflammation of the joint is known as arthritis. Arthritis has little to do with the lack of calcium. Therefore taking calcium will not reduce joint pain! 

So if lack of calcium does not cause joint pain, then what does a lack of calcium do? A decrease in the calcium content of bones is typically called osteoporosis (different from osteo-arthritis) There are other disorders of calcium like osteomalacia and rickets but these are rare. Osteoporosis affects women after menopause. It is the lack of female hormones (estrogen and progesterone) that leads to osteoporosis. Osteoporosis also affects men but at a later age and less commonly. Osteoporosis is a silent disease. That means that it causes very few or no symptoms. Many patients of osteoporosis will not know that they are suffering from it! This is similar to medical illnesses like diabetes and hypertension (high BP). Time and again the first symptom of osteoporosis is a fracture of the hip or a vertebra (spine fracture). Rarely osteoporosis may cause bone or muscle pain or tenderness (pain on pressing the bone). 

If osteoporosis is a silent disease, how do doctors and patients diagnose it? Like diabetes early diagnosis of osteoporosis is critical as treatment can reduce fracture risk. Earlier it was difficult to diagnose osteoporosis. Doctors would get some idea of bone strength by looking at x-rays of the patient. However x-rays are a crude test as they show osteoporosis only in the advanced stages. By then it is too late! Measuring the blood calcium levels gives no indication of the strength of bones or the level of calcium in the bones. Nowadays technology has improved. A DEXA scan is currently the gold standard for measuring bone mineral density (BMD). DEXA scan checks the density in the lower back and hip which are the critical areas. DEXA scan is a computerised X-ray based test. Ultrasound of the wrist or heel can also be done. Ultrasound is popular as it is portable (used frequently in patient camps) and cheaper. But ultrasound is less accurate and the wrist and heel density may differ from the density in the back and hip. I do not recommend treatment decisions to be made on ultrasound based bone density results. Does everybody need to do a DEXA scan? The answer is NO! The World Health Organisation (WHO) recommends BMD testing in all postmenopausal women above 65 years of age. In post menopausal women less than 65 and premenopausal women, density testing is required only if they have certain medical risk factors (ask your doctor). There is no need for healthy premenopausal women to do a DEXA scan or other BMD testing. BMD testing is also not recommended for healthy men with no risk factors. 
To conclude, I advice my readers to be smart about calcium supplements. Taking unnecessary supplements in the hope of reducing pain is a waste of money. At the same time one should be alert about osteoporosis. Timely BMD testing by DEXA scan is the key. If osteoporosis is diagnosed by a DEXA scan, then treatment with supplements is imperative.
BMD measurements have today become essential for fracture prevention and osteoporosis treatment, but due care is needed in utilising this asset.

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