OSTEOPOROSIS: ARE YOU LOSING BONE?
Unfortunately, because osteoporosis is a silent disease, it has always been a problem that there are few outward signs until bones have become so weak that they can suddenly fracture.
Have you measured your height lately? Are you shorter than you used to be, or stooped? As spinal vertebrae fracture, collapse and are crushed together, height is lost between hips and neck and your posture changes. Height measurements should be a part of your routine medical examinations, with every doctor’s surgery having a scale on the wall for measurements to be made regularly. Do you know how tall you were at skeletal maturity, about the age of twenty-five? You can roughly calculate your early adult height by measuring your armspan, since that width is usually (but not always) nearly equal to your earlier height at adulthood. Deduct this armspan measurement from your present head-to-heel height for a rough estimate of height loss.
Do you have transparent skin? On the back of your hand, if the skin is loose and lacking pigment so you can see the edges of small as well as large veins, this transparency indicates collagen deficiency in the outer layers of your skin. As one of the components of bone is collagen, it has been concluded that skin thickness has a correlation with bone thickness. However, this is also an indication of rheumatoid arthritis. Skin thickness can be measured with calipers in your doctor’s surgery.
Do you have gum disease? Gum disease can be a sign of poor dental hygiene – but sometimes it is a warning of osteoporosis. Many adults, especially middle-aged women, lose their teeth with pyorrhoea. Periodontal disease or pyorrhoea affects the tissues supporting your teeth – the gums, ligaments attaching teeth to your jaw and sometimes the alveolar bone. Where there is loss of bone in the jaw, gums can recede, teeth are not securely held in their proper place and change position, inviting bacteria to the exposed areas between gums and teeth. If too much alveolar ridge is lost, even dentures cannot be properly seated. Ask your dentist about X-rays of your jaw as they can be a useful indication of the bone density elsewhere in your body.
If you think your bones may be at risk, other tests can be done to evaluate bone mass, depending to some extent on the equipment available in your neighbourhood, and how your physician prefers to approach the problem. Sometimes doctors will take blood and urine samples for analyses of calcium in the blood and calcium excreted in urine and thus lost from your body. These tests do not provide a diagnosis of primary osteoporosis with any degree of certainty, because of variations resulting from food intake, metabolism, heavy use of laxatives, and the possibility of other bone disease.
Although spinal, hip and jawbone X-rays are frequently used, they are perhaps not sufficiently sensitive to discern early bone loss, the problem being that in standard X-ray imaging the hard dense outer layer of bone tissue (cortical bone) can hide the inner honeycomb-type bone (trabecular bone). With osteoporosis, cortical bone gets thinner, and trabecular bone more porous, but unless 30 per cent of bone mass is lost, radiologists might have difficulty in detecting osteoporosis. In some cases, X-rays may reveal that one or more vertebrae have already fractured, even though you have not been conscious of any back pain. Many patients with osteoporosis do have pain, however: either a chronic ache along the spine or pain from spasm in the back muscles. This occurs when the muscles of the back must take an increased share of the load of supporting the upper half of the body, after the spine has partially collapsed. Then the muscles will ‘complain’ periodically.
If you live in a large city or near a big hospital, the preferred method of evaluation is a CAT scan. Computerized Axial Tomography is a way of seeing bones with multiple X-ray exposures combined by computer into one picture. By modifying a CAT scanner, which produces a cross-sectional image of your body, or part of your body, doctors can get a reading on the amount of bone density. A modified scanner, differentiating and separating images of trabecular (where bone loss is more severe) and cortical bone, can tell the amount of bone mineral present, whether there is some degree of osteoporosis, and monitor it so there are no further complications.
In certain clinics, it may be possible to have tests using other types of X-ray equipment: radiogrammetry, radiographic photo-densitometry or photon absorptiometry, to measure bones in fingers or forearms, since if you do have osteoporosis it will be occurring in many places simultaneously.
Single proton absorptiometry measures the density of forearm bones or the heel. The bone is penetrated by a narrow beam of photons from a radioactive source. Radiation exposure is quite low, under lOmrem. This test is useful if you are over 75, and if you have had large changes in bone density due to medical treatments.
Dual photon absorptiometry is similar, except that the radioactive source produces two beams, for a more precise measurement. It can be used to measure the hip, the spine and other skeletal sites. Radiation exposure is about 30mrem. This test is appropriate if you are middle-aged, because it measures the hip and spine. However, it is less useful than a CAT scan if you are over 75 or have calcium deposits or bone degeneration around the spine.
Dual energy radiography is still being developed, but promises greater precision and lower radiation. Total body neutron activation analysis, performed in a very few research laboratories, is a method for measuring the total calcium in your body, and your skeleton in particular.
If your doctor considers further examination necessary, he will investigate what is available in your area, what diagnostic equipment is in nearby clinics, hospitals and research centres, and the costs involved if you have private treatment. Usually at least two separate tests are necessary, to discover the rate at which your body is being depleted of calcium and your rate of bone loss.
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