Densitometry of bones and osteoporosis is another chance to learn in advance about the disease

Osteoporosis is a pathology in which the bones lose calcium and become brittle. In the presence of the slightest traumatic factor, they can deform or break. Mistakenly believe that this disease develops in people whose body receives insufficient amounts of calcium. It is not true. Osteoporosis develops even with an excess of this trace element in food. The cause of increased brittleness of bones is insufficient absorption of calcium by bones or its "washing away".

Etiology of osteoporosis

The density of bone tissue depends on the amount of sex hormones. In men, testosterone is more than in women, so their bones are much thicker and stronger. Because of this, osteoporosis is more often diagnosed in women, especially in menopause, because at this time the level of hormones is significantly reduced.

Other reasons for osteoporosis include hypodynamia, lack of vitamin D, wine consumption, smoking, the presence of chronic diseases (diabetes mellitus, lesions of the thyroid gland, chronic liver and kidney pathologies).

How to identify osteoporosis?

If a person notes increased fatigue and bone pain, changes in posture and gait, hair loss and deterioration of the teeth, as well as frequent fractures, recommend densitometry. This is a quick and absolutely painless examination that allows you to identify and measure the loss of bone density, as well as determine the content of minerals and assess the risk of fractures. This examination is the most sensitive method of early diagnosis of osteoporosis.

The essence of densitometry is the transmission of bone tissue through invisible X-rays. At the same time, a low dose of ionized radiation is applied in the form of two energy flows, which allows for a quick and accurate examination.

It should be noted that bone densitometry is characterized by a dose of radiation that is minimized (it is less than 1/10 of the dose that patients receive when performing standard chest x-ray).

When densitometry is performed

Indications for this survey are the following:

• Early menopause or menopause, which occurs in women after cessation of menstruation;
• The presence of renal insufficiency;
• Chronic liver pathologies;
• Long-term treatment with glucocorticoids;
• A syndrome of reduced absorption of nutrients, which leads to a deficiency of calcium;
• Bone densitometry is also performed in the presence of rheumatoid arthritis, hyperparathyroidism and hyperadrenocorticism, as well as hypothyroidism and diabetes mellitus.

If fractures are observed with minor injuries, this is also an indication for this survey. It is believed that a violation of the integrity of the bones in osteoporosis reduces the life expectancy of patients even more than oncological diseases, so timely detection of the disease is extremely important. It should be noted that in some cases hereditary forms of this pathology are found.

Bone densitometry: the main types

There are various methods for detecting osteoporosis, but their use is rather limited. So, various modifications of MRI are expensive, quantitative computed tomography gives a high dose of radiation, studies of the corresponding biochemical indicators of metabolism in bones are characterized by significant variations in regulatory data, and bone biopsy patients feel discomfort. When osteoporosis is diagnosed, densitometry is the most popular method.

Three main methods are used, which were developed specifically to detect this disease:

• X-ray absorptiometry;
• Ultrasonic densitometry;
• Peripheral computed tomography (has a significant drawback - it does not allow to evaluate the state of the bones of the axial skeleton).

For the correct choice of the method of investigation and a correct evaluation of the results obtained, the features of clinical manifestations are taken into account. Adequate diagnostic criteria are also taken into account.

Principles of evaluating the results of densitometry

To describe the data obtained after the survey, the term "osteopenia" or "osteoporosis" is used. They should not be considered as a clinical diagnosis, but only as a symptom that can accompany any lesion of the skeleton with a decrease in its density. It should be noted that bone densitometry is not performed for a clear diagnosis, but for detecting the risk of fractures in patients.

In this case, the hardware software (densitometer) compares the results and the selected database, and the difference reflects statistically. The number of standard deviations is determined, which is called the T-test (used for comparison with young people of the same sex as the patient) or Z-criterion (for comparison, a group of people of the appropriate age, sex or weight is taken).

If the T-test is not more than 2.5 SD, then this corresponds to osteopenia, if the results are lower than this indicator, then they speak of osteoporosis. These values are considered "threshold" values. This should be taken into account for the correct interpretation of the results of densitometry.

X-ray densitometry

Technically, with the help of X-ray irradiation, you can examine most of the bones. As a rule, densitometry of the spine (its lumbosacral section), as well as the hip joint, where the fractures develop most often against the background of osteoporosis, is performed. Also determine the density of bone tissue of the thigh and forearm or conduct a full body densitometry. This survey allows you to determine the content of minerals in individual parts of the body or throughout the body.

In the past, the isotope absorptiometry method was used to estimate the bone mass and the content of mineral compounds, the principle of which is the effect of gamma particles and the evaluation of their absorption. An important drawback of such a survey was a significant radiation load. Subsequently, two-photon X-ray absorptiometry, which was highly sensitive and less harmful to patients, was used. To date, with its help, only 2-3% of bone loss is detected, so this examination can be used to examine postmenopausal women for early detection of osteoporosis.

Ultrasound densitometry

This type of examination is conducted to assess the strength of bones. Consideration is given to density, microstructure and elasticity, as well as the thickness of the cortical layer. An important advantage of such a survey is the absence of radiation load. Given the safety of this procedure, it can be repeated without any restrictions.

It must be said that such a densitometry is based on the property of ultrasonic waves to spread over the surface of the bone or to dissipate in bone tissue. In this case, it is possible to determine the elasticity, density and rigidity of the bone.

It should be noted that ultrasound bone densitometry is used only for examination of the peripheral skeleton. Most often, this method is used to examine the heel and tibia, the patella or the phalanges of the fingers. Most instruments determine the speed of ultrasound transmission or its weakening, which indicates not only the density of bone tissue, but also the presence of trabeculae or microdamages.

Conclusion

Regardless of how osteoporosis is treated (in the form of a symptom or disease), densitometry can determine the risk of fractures. It should be remembered that the choice of the site of examination is extremely important, as the density or mineralization of bones can not be the same for the entire skeleton.

To make the right choice, you need to know the following patterns:

• Trabecular substance is affected by menopause, hypogonadal syndrome or steroid imbalance;
• The primary damage to the cortical bone is observed in senile, hyperthyroid, diabetic osteoporosis;
• If the patient develops a disease in childhood or adolescence, at which the growth of the skeleton is disturbed, then systemic bone defects are diagnosed. They are accompanied by damage to both bone layers.

It is necessary to know that there is a tendency to "spread" osteoporosis from the axial skeleton to its peripheral areas, therefore, for early diagnosis, the vertebrae should first be examined. Free densitometry, unfortunately, is rare, since this survey is usually conducted in private clinics and requires appropriate equipment.