The role of densitometry in the diagnosis of osteogenesis imperfecta

Bone densitometry is a non-invasive method which uses differences in gamma or X-ray absorption in bones or soft tissue in order to directly measure bone mineral density (expressed in g.) and to indirectly measure bone density (expressed in g/cm2). The most important regions for measuring bone mass are the spine, femur and forearms. These localisations are of the highest risk for fractures when there is low bone mass. In order to measure bone density today Dual Energy X-ray Absorptiometry (DEXA) is used, where the source of radiation is an X-ray tube. This is the leading method for bone density measurements. Bone densitometry has become the generally accepted method for diagnosing patients with metabolic bone disorders, and also for bone metabolism research. The greatest incentive for the development of this method came from osteoporosis research where precise determining of bone mass is essential. Densitometry is also used for diagnosis of osteogenesis imperfecta (OI) because the consequence of OI is osteoporosis. OI is a genetic disease where due to lack of or poor collagen quality bones are very brittle and have less density. The most common feature of the bone disorder in OI is low bone density and this is the main reason why fractures occur. Densitometry can help to evaluate developments in bone changes and the risk of fractures in patients with OI. This method is also used to assess therapy results. The method is non-invasive. During this procedure the patient must be motionless which is not a major problem since it only lasts a couple of minutes. The radiation burden is low. The results of densitometry must be interpreted with the results of other investigations.