Ch.21 - Recognizing Abnormalities of Bone Density Flashcards
Role of conventional radiograph, CT, MRI:
Conventional radiograph –> Cortex is best seen in tangent.
CT –> Entire cortex is visualized.
MRI –> Particularly sensitive to assessment of the marrow.
Osteoblastic metastases, esp. from carcinoma of the prostate and breast, can produce:
FOCAL or GENERALIZED increase in bone density.
Other diseases that can increase bone density:
- Osteopetrosis.
- Avascular necrosis of the bone.
- Paget disease.
Hallmarks of Paget disease:
- Thickening of the cortex.
- Accentuation of the trabecular pattern.
- Enlargement and increased density of the affected bone.
Osteolytic metastases, esp. from lung, renal, thyroid, and breast cancer, can produce:
Focal areas of decreased bone density as can solitary plasmacytomas, considered to be a precursor to MM, the MC primary tumor of the bone.
Examples of diseases that can cause a generalized decrease in bone density include:
- Osteoporosis.
- Hyperparathyroidism.
- Rickets /osteomalacia.
Osteoporosis:
- Low bone mineral density and is most often either postmenopausal or age-related.
- Predisposes to pathologic fractures.
Pathologic fractures are those that occur:
With minimal or no trauma in bones that had a pre-existing abnormality.
Examples of diseases that can cause focal decrease in bone density include:
- Metastases.
- MM.
- Osteomyelitis.
Modality of choice in screening for skeletal metastases:
Radionuclide scan.
MRI –> To solve specific questions related to a lesion’s composition and extent.
There must be almost a …% reduction in the mass of bone in order for a difference in density to be perceived on conventional radiographs.
50%.
–> MRI is much more sensitive to the presence of medullary metastatic disease.
Causes of osteoblastic metastases:
- Prostate (MC in men).
- Breast - usually osteoLYTIC, but can be osteoBLASTIC, especially if treated.
- Lymphoma.
- Carcinoid tumors.
Causes of osteolytic metastases:
- Lung cancer –> MC in men.
- Breast cancer –> MC in females.
- RCC.
- Thyroid carcinoma.
Insufficiency fractures:
TYPE of a PATHOLOGIC fracture in which mechanically weakened bone fractures from a normal or physiologic stress.
Insufficiency fractures - MC in post menopausal women 2o to:
Osteoporosis.
Insufficiency fractures - Common sites:
- Pelvis.
- Thoracic spine.
- Sacrum.
- Tibia.
- Calcaneus.
Unlike other fractures that manifest themselves by a lucency in the bone, most insufficiency fractures display:
A sclerotic band (representing healing) on conventional radiographs.
Focal decrease in bone density:
- Metastatic disease to bone (osteolytic).
- Multiple myeloma.
- Osteomyelitis.
Metastatic disease to bone:
- Metastases to bone are far more common than primary bone tumors.
- Osteoblastic + Osteoclastic.
- UNCOMMON distal to the elbow/knee - when present, think widespread metastatic disease from lung/breast.
Study of choice for detecting skeletal metastases:
Radionuclide bone scan.
Diffuse decrease in bone density:
- Osteoporosis.
- Hyperparathyroidism.
- Rickets.
- Osteomalacia.
Some causes of vascular necrosis of the bone:
Intravascular –> SCA, polycythemia vera.
Vascular –> Vasculitis (lupus and radiation-induced).
Extravascular –> Trauma (fractures).
Idiopathic –> Exogenous steroids + Cushing/Legg-Calve-Perthes disease.
Focal increase in bone density:
- Carcinoma of the prostate (which can also cause a diffuse increase in bone density).
- Avascular necrosis of bone.
- Paget.
Diffuse increase in bone density:
- Carcinoma of the prostate (which can also cause a focal increase in bone density).
- Osteopetrosis.