1. Upper left = normal
2. Upper right = misset fracture (acquired)
3. Lower left = "gracile" (thin) bone caused by polio
4. Lower right = achondroplasia, congenital abnormality in longitidunal growth ("Dwarfism)

Bone density abnormalities

1. Upper left = Normal
2. Upper right = osteoporosis; note prominent trabecular pattern, and loss of cortical density
3. Bottom left = Paget's disease (thickened cortical and trabecular bone)
4. Bottom right = bone metastases from prostate cancer (foci of localized density increase)

Localized destruction of bone

1. Upper left - normal
2. Upper right - Rheumatoid arthritis (erosion from extrinsic site). Sharp margins = slow process
3. Lower left - Enchondroma (slow growing, cortex intact, easy to determine where normal ends and lesion begins
4. Lower right = lytic metastisis (intrinsic, rapid destruction

Change in soft tissue

1. Upper left = normal
2. Upper right = hemorrhagic effusion
3. Lower left = "housemaid's knees" (bilateral ossification of anterior soft tissue)
4. Lower right = osteosarcoma (cloud-like density in posterior soft tissue and periostal new bone extending from cortex)

Trauma to elbow. Note outline posterior to olecranon fossa = fat pad. Radial intrarticular fracture (right) most likely caused hemoarthrosis.

Note, most common pediatric humeral fracture = supracondylar, adult = radial head

Dislocation of right femoral head, with acetabular fracture. In this case, trauma is from vehicular accident that drives the femur up

CT provides most sensitive indicator of pelvic/acetabular fx

1. Blood flow phase - "hotter" sites indicate increased blood flow, possibly due to inflammation or trauma. Taken immediately post-injection.
2. Blood pool phase - pooling of venous blood. Taken 3-5 minute post-injection
3. Delayed skeletal phase - uptake of MDP by bone. Typical of fracture (and sometimes lytic, non-multiple myeloma metastases). Taken 2 hours post-injection.

Overall, scan is used to indicate stress fractures that may take long time to develop (e.g. jogging related)

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Note: left knee

Mnemonic = Pb Ktl (lead kettle)

Prostate = blastic (induces bone formation)

Breast = mixed

Kidney, thyroid, lung = lytic (causes bone destruction)

Note: multiple myeloma causes "punched-out" holes in bone

1. Upper left = normal
2. Upper right = lytic metastases (in this case, metastic lung cancer)
3. Bottom = blastic metastases (prostate cancer)

Arthritis

1. Upper left - normal
2. Upper right - OA. Note lack of joint space in thumb IP, along with osteophyte (bony spur), and lack of space in DIPs.
3. Bottom - RA. Juxta-articular erosions in MCP. DIPs spared.

1. Highly specific test is Indium-labeled WBC's
2. On MR, inflamed, infected sites will be darkened on T1 and bright on T2

Heavy metal poisoning.

Radiograph taken from 8-year old child. Note discrete sclerotic band of increased density near metaphesis, due to absence remodeling. Density indicates concentration of lead, width indicates time of exposure

Morquio's disease

Note the genu valgus (inward bending of knee) and "beaked" vertebrae. Autosomal recessive disorder.

Osteogenesis imperfecta

Type I collagen abnormality --> brittle bone disease. Presents with multiple fractures, joint laxity, changes in eye, ear, teeth and skin.

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Osteopetrosis

"Marble bone" disease. Radiodense, stone-like bone, with abnormal weakness (chalk-like). Carbonic anhydrase activity --> osteoclast abnormality. Presents with Erlemeyer's flask deformity.

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Osteochondroma (ectopic bone plate)

Peak age = 2nd decade

Common location = distal femur

Proliferation of cartilage, histology mimics normal growth plate. Usually in metaphyseal location.

Endochondroma

Thin cortex, typically in the small bones of the hand. Histology show hypocellular tumor...

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Chondroblastoma

Chicken-wire appearance; occurs in 2nd decade, most commonly in proximal humerus, distal femur, proximal tibia. One of few cartilage tumors to appear in epiphysis

Chondrosarcoma

Malignant. Appears in adults. Most common location = big flat bones, like acetabular region, central skel and verebrae. Intramedullary in metaphysis or diaphysis. Presents with PAIN. Pleomorphic (nuclei all shaped differently)

Osteoid osteoma

Peak age = 2nd decade. Lucency appears in diaphysis, usually less than 2cm. Proximal femur and femoral neck. Histology --> interlacing network of trabeculae rimmed by osteoblasts. Pain worse at night.

Osteoma

Typically presents with propoptosis, if on skull or nasal sinuses.

Osteoblastoma

Very rare, but unique in that it present commonly in vertebrae with possible neurologic side effects. Histology similar to osteoid osteoma.

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Osteosarcoma

Bimodal age distribution. Most common location is distal femur or proximal tibia. Metaphysis of long bone. Pain, Codman's triangle (tumor breaks through cortex and lift periosteum). Histology = pleomorphic, abundant mitotic figures

Aneurysmal bone cyst

Occurs in second decade, most commonly in femur, tibia, and vertebra.

Non-ossifying fibroma

No bone formation, characteristically on the circumference of metaphysis.

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Patient presents with endocrinpathy

Fibrous dysplasia

Multifocal, arises during growth of skeleton. Endocrinpathy includes sexual precocity, hyperthyroidism, pituitary adenomas

Ewing's sarcoma

Classic "onion-skinning" on X-ray. Chromosomal translocation between 11;22 (11+22 = 33, Patrick Ewing's number). Second most common malignant bone tumor in children after osteosarcoma. Dark blue histology. Arises in diaphysis of long tubular bones.

Giant Cell Tumor

Uncommon, but locally aggressive, occurs in third decade. Histology = sea of mononuclear cells. Occurs on end of bone.

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Osteoporosis

Deficiency in osteoclasts. Characterized by low bone mass. Porous. Occurs primarily in postmenopausal females. Vunerable to fracture.