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Flashcards in Bone and Bone Disease Deck (50):
1

Woven Bone

disorganized structure
irregular osteocytes

2

lammellar bone

organized into osteons

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osteons

lamellar bone structure
haversian canal with surrounding osteocytes arranged in rings (lamellae) - concentric rings

4

haversian canal

Contains blood vessels that feed osteon
communicates with surrounding osteocytes via canaliculi

5

spongy bone

trabecular/ cancellous bone
thinner
trabecullar or reticular pattern
location = epiphysis of long bones (ends) & vertebral bodies

6

compact bone

cortical bone
hard, long, smooth bone
ex: humerus, femur, diaphysis

7

endochondral ossification

longitudinal bone growth (ex: femur, humerus)
chondrocytes initially form a cartilaginous model
osteoclasts and osteoblasts follow, replacing cartilage with woven bone
woven bone is later remodeled into lamellar bone

8

membranous ossification

flat bone growth (skull, facial bones, axial skeleton)
woven bone is formed directly by the osteoclasts and osteoblasts without cartilage.
woven bone is later remodeled to lamellar bone

9

origin of osteoblasts

bone-producing cells
origin = mesenchymal stem cells in the periosteum

10

Hydroxyapatite

forms bone mineral
inorganic component of bone

11

achondroplasia

DWARFISM = failure of longitudinal bone growth
PE: short limbs, large head (normal membranous ossification)
path: constitutive activation of fibroblast growth factor receptor (FGFR3) = inhibits chondrocyte proliferation
genetics: 85% sporadic & ass w/ advanced paternal age, also shows autosomal-dominant inheritance

12

Osteoporosis

trabecular (spongy) bone loses mass and interconnections despite normal bone mineralization (hardness) and lab values
Effects: vertebral crush fractures (acute back pain, loss of height, kyphosis)

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Osteoporosis Type I

post-menopausal women
DECREASED estrogen --> increased bone resorption
etiology: RANK ligands (osteoblasts)

14

RANK ligand and RANK receptor

RANK ligand = on osteoblasts
RANK receptor = on osteoclasts
RANK ligand and receptor interaction promotes osteoclast activity

15

estrogen effects on RANK

decreased estrogen = promotes increased RANK receptor expression (osteoclasts)-->
increased RANK ligand and receptor interaction and INCREASED bone resorption

16

Type II Osteoporosis (Senile)

man or woman > 70 YO
presentation: compression fractures, femoral neck fracture, hip fracture, distal radius (Colles' fracture - fall onto outstretched hand)
signs/symptoms: acute back pain, loss of height, kyphosis

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prophylaxis osteoporosis

exercise (weight-baring)
calcium ingestion < 30 YO

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osteoporosis treatment

Selective Estrogen Receptor Modulators (SERMs)- blocks estrogen from binding to bone estrogen receptors
Calcitonin = causes less bone resorption
pulsatile PTH (severe cases)
bisphosphonates (most common)
DON'T GIVE Glucocorticoids

19

Bisphosphonates

-dronate
etidronate
pamidronate
alendronate
risedronate
zoledronate (IV)

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bisphosphonate mechanism

structural analog of pyrophosphate (component of hydroxyapatite) that inhibits osteoclast activity
reduce both formation and resorption of hydroxyapatitie (bone mineral)

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bisphosphonate clinical use

postmenopausal osteoporosis
Paget's disease of the bone
malignancy-associated hypercalcemia

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bisphosphonate adverse effects

corrosive esophagitis (drug taken while sitting upright) -except zoledronate (iv)
nausea
diarrhea
osteonecrosis of the jaw

23

osteopetrosis (marble bone disease)

failure of normal bone resorption
thick, dense bones = prone to fracture
abnormal osteoclast function (carbonic anhydrase II deficiency)
normal lab values - normal serum Ca, phosphate, Alk phos
decreased bone marrow = anemia, thrombocytopenia, leukopenia
extramedullary hematopoiesis = hepatomegaly and splenomegaly
narrowing skull foramina = CN impingement and CN palsies (visual and hearing loss)
x-ray = Erlenmeyer flask bones (flare out)

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erlenmeyer flask bone on x-ray

osteopetrosis
thickened, dense bones (prone to fracture) due to osteoclast function defect

25

osteomalacia

defective mineralization/calcification of osteoid --> SOFT BONES
normal bone mass
Vit. D deficiency Adults --> decreased Ca levels --> increased PTH, decreased serum phosphate
reversible when vit D replaced

26

rickets

vit. D déficience in childhood
can cause life long bone deformation
cranial tabes = failure of fontanelles to close
rachitic rosary = thickened costochondral junctions

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osteomalacia histology

normal osteoid matrix accumulation around trabeculae (normal osteocytes)
absent mineralization

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cranial tabes

failure of fontanelles to close
seen in Rickets = vit D deficiency in childhood

29

rachitic rosary

prominent knobs of bone at the costochondral joints
appearance of large beads under the skin of the rib cage
due to a deficiency of calcium resulting in lack of mineralization and an overgrowth of costochondral joint cartilage
cause: rickets, or other forms of Ca deficiency (hypoparathyroidism)

30

Paget's disease (osteitis deformans)

abnormal bone architecture due to increased osteoblastic and osteoclastic activity
increased bone formation and resorption
cause: paramyxovirus suspected
labs: normal serum Ca, phosphorus, PTH, ELEVATED Alk phos (ALP)

31

paget's disease histology

mosaic bone pattern - bone breakdown and reformation
osteolytic processes followed by osteoblastic processes

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Paget's disease morphologic stage

hat size increases = extra bone formation in skull
hearing loss = narrowing of auditory foramen

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late complications of Paget's disease

arteriovenous malformations and shunting within bone
can cause high output cardiac failure (CHF)
can lead to osteogenic sarcoma

34

polyostotic fibrous dysplasia

bone is replaced by fibroblasts, collagen, and irregular bony trabeculae
associated with McCune-Albright syndrome (most common cause)

35

McCune Albright Syndrome

multiple unilateral bone lesions associated with endocrine abnormalities (precocious puberty) and Cafe-au-lait spots on the skin

36

osteitis fibrosa cystica

bone disease associated with chronic kidney disease (brown tumors of the bone)
cause: chronic kidney disease --> decreased vit D production (1,25-D activated in kidney)
compensatory increase in PTH
elevated Alk Phos due to elevated osteoblast activity

37

lab values in osteitis fibrosa cystica

elevated PTH
hypercalcemia
hypophosphatemia
elevated Alk phos (osteoblast activity)

38

benign bone tumors

osteoma

39

osteoma

benign bone tumor
associated with Familial Adenomatous Polyposis (FAP)
findings: numerous colonic polyps, jaw osteoma

40

osteoid osteoma

benign bone tumor
histo: interlacing trabeculae of woven bone, surrounded by osteoblasts
x-ray = radiolucent center (central nidus of osteoid) surrounded by a thin rim of bone (dense white rim)
features: < 2cm
location: proximal tibia and femur (knee area)
most commonly in men < 25 YO

41

osteoblastoma

benign primary bone tumor
histo: interlacing traveculae of woven bone, surrounded by osteoblasts
location: vertebral column

42

Giant Cell Tumor (osteoclastoma)

location: epiphyseal end of long bones (end of long bones) - distal femur, proximal tibial region (knee)
incidence: 20-40 YO, Men > women
benign, locally invasive
x-ray = double bubble / soap bubble appearance (local bone break down)
histo: spindle shaped cells with multinucleate giant cells

43

Osteochondroma (exostosis)

most common benign tumor
sticks out with a cartilaginous cap (exostosis)
Men < 25 YO
location: metaphysis of long bones
malignant transformation (chondrosarcoma) rare

44

enchondroma

benign, cartilaginous tumor
intramedullar space
location: small bones (hands and feet)

45

Osteosarcoma (osteogenic sarcoma)

malignant
2nd most common bone malignancy (melanoma #1)
men, ages 10-20 YO
location: metaphysics of long bones (distal femur, proximal tibia)
poor prognosis

46

risk factors for osteosarcoma

Paget's disease of bone
bone infarcts
history of bone radiation
familial retinal blastoma

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osteosarcoma x-ray appearance

sunburst pattern = periosteal elevation due to inflammation) = Codmann's triangle

48

Ewing's sarcoma

aggressive, fast-growing malignant bone tumor
boys < 15 YO
location: diaphysis of long bones, pelvis, scapula and ribs
histo: anaplastic, small blue cells
tx: good response to chemo
x-ray: "onion skin" appearance in bone

49

chondrosarcoma

malignant cartilaginous tumor
men 30-60 YO
pelvis, spine, scapula, humerus, tibia or femur
may be primary origin or from osteochondroma
expansive glistening mass within the medullary cavity

50

Ewing's sarcoma genetics

11;22 translocation
neuroendocrine differentiation - confirmed by positive S-100 protein and neuron-specific enolase immunohistochemical stains
often contains glycogen