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.
Bone consists of:
A cortex of compact bone surrounding a medullary cavity containing cancellous bone arranged as trabeculae, separated by blood vessels, hematopoietic cells, and fat.
Almost all examinations of bone start with …?
Conventional radiographs obtained with at least 2 views exposed at 90 degrees angle to each other –> Orthogonal views.
Problems with conventional radiographs?
- Cannot visualize the entire circumference of a tubular bone.
- They are not particularly sensitive for demonstrating musculoskeletal soft tissue abnormalities, other than soft tissue swelling.
What is excellent to study bone marrow pathology?
MRI.
Cortical bone in MRI?
Has a very LOW signal intensity on conventional MRI.
MRI - Bone marrow disorders could be divided into 4 categories:
- Reconversion.
- Marrow replacement.
- Myeloid depletion.
- Myelofibrosis.
Reconversion refers to …?
Reversal of the normal conversion of the marrow cells so that red marrow repopulates bone from which it had been replaced by yellow marrow.
–> Chronic anemias (SCA) is an example.
Recognizing a generalized INCREASE in bone density:
- On conventional radiographs/CT –> Overall whiteness (sclerosis).
- Diffuse loss of visualization of the normal network of bony trabeculae in the medullary cavity –> Replacement by bone-producing elements.
- Loss of visualization of the normal corticomedullary junction.
Increase in bone density - Why is there loss of visualization of the normal corticomedullary junction?
Because of the abnormally increased density of the medullary cavity relative to the cortex.
Prototype for generalized increased in bone density?
Diffuse, blood-borne, metastatic disease from carcinoma of the prostate.
Metastatic disease to bone occurs in over …% of autopsied patients with carcinoma of the prostate.
80%.