Osteoporosis

Generalized osteoporosis may be age-related (senile and postmenopausal osteoporosis) or may accompany endocrine disorders (acromegaly, hyperparathyroidism, hyperthyroidism, Cushings disease), pregnancy, heparin administration or alcoholism. Involvement of the axial skeleton and proximal portions of the long bones of the appendicular skeleton predominates. In the spine not only osteopenia but also changes in vertebral contour occur. Usually a uniform decrease in radiodensity is noted. Differentiating generalized osteoporosis from osteomalacia radiographically may be extremely difficult.

One form of generalized osteoporosis is idiopathic juvenile osteoporosis, an uncommon, self-limiting disease of childhood. Spinal osteoporosis, vertebral collapse, and kyphosis are characteristic features. Also typical is metaphyseal injury, especially about the knees and ankles. Metaphyseal lucent lesions may lead to complete fractures with subsequent deformities. Generalized osteoporosis may also accompany plasma cell myeloma, Gauchers disease, glycogen storage disease, anaemias, nutritional deficiencies, diabetes mellitus, immunodeficiency states and chronic liver disease.

Regional osteoporosis occurs in osteoporosis of disuse or immobilization, reflex sympathetic dystrophy, transient osteoporosis of the hip and regional migratory osteoporosis. Changes predominate in the appendicular skeleton. A more aggressive type of bone resorption in these conditions can lead to cortical bone changes at endosteal, intracortical and subperiosteal bone envelopes and to spongy bone changes at subchondral and metaphyseal locations.

Localized osteoporosis is commonly associated with focal skeletal lesions, such as neoplasm and infection.

Radiographic manifestations of osteoporosis include changes in radiolucency, trabecular pattern, and shape or vertebral bodies in the spine (wedge-shaped vertebrae, compressed vertebrae, fish vertebrae), Schmorls nodes, acute and insufficiency fractures and bone bars (reinforcement lines).

In the proximal portion of the femur, five anatomical groups of trabeculae can be identified, and patterns of trabecular loss can be used as an index of presence and severity of osteoporosis (Singh index).

In the tubular bones, bone resorption may be distinguished in three sites (endosteal envelope, intracortical [haversian] envelope and periosteal envelope). These changes are best detected with magnification radiography and quantitated with radiogrammetry.

MR im transient osteoporosis of the hip as decreased signal intensity on T1-weighted sequences and increased signal intensity in the corresponding region on T2-weighted sequences. The patient commonly has associated joint effusions in the affected hip. Chemical shift fat suppression and STIR imaging techniques can be effective in the detection of transient bone marrow oedema.

Osteoporosis circumscripta is one of the radiographic features of the cranial vault in Pagets disease.

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