Bone Conditions

Question 1

Describe a greenstick fracture

Answer 1

Incomplete, extends partway thro width of bone following bending stress;
bone fails on tension side; compression side intact (compare to torus fracture)

Question 2

Describe Torus (buckle) fracture

Answer 2

Axial force applied to immature bone = cortex buckles on compression (concave) side + fractures
Tension (convex) side remains solid (intact)

Question 3

What is Achondroplasia

Answer 3

Failure of longitudinal bone growth (endochondral ossification) = short limbs
Membraneous unaffected (large head relative to limbs)
Most common cause of short-limbed dwarfism

Question 4

How does achondroplasia occur

Answer 4

Constitutive activation of fibroblast growth factor receptor (FGFR3) inhibits chondrocyte proliferation
>85% of mutations sporadic (AD, homozygosity lethal)

Question 5

Risk factor for achondroplasia

Answer 5

Increased paternal age

Question 6

What is osteoporosis

Answer 6

Trabecular (spongy) and cortical bone lose mass despite normal bone mineralization and lab values (serum Ca, phosphate)

Question 7

How does osteoporosis occur

Answer 7

Increased bone resorption (increased osteoclast # and activity) related to decreased estrogen levels and old age

Question 8

Name causes of secondary osteoporosis

Answer 8

Drugs (eg, steroids, alcohol, anticonvulsants, anticoagulants, thyroid replacement therapy) or other conditions (eg, hyperparathyroidism, hyperthyroidism, multiple myeloma, malabsorption syndromes, anorexia)

Question 9

How is osteoporosis diagnosed

Answer 9

Bone mineral density measurement by DEXA at the lumbar spine, total hip, and femoral neck, with a T-score of ≤ −2.5/by a fragility fracture (eg, fall from standing height, minimal trauma) at hip or vertebrae

Question 10

Prophylaxis for osteoporosis

Answer 10

Regular weight-bearing exercise and adequate Ca2+ and vitamin D intake throughout adulthood

Question 11

Tx for osteoporosis

Answer 11

Bisphosphonates, teriparatide, SERMs, rarely calcitonin; denosumab (monoclonal antibody against RANKL)

Question 12

What can osteoporosis lead to

Answer 12

Vertebral compression fractures (acute back pain, loss of height, kyphosis
Can also present w fractures of femoral neck, distal radius (Colles)

Question 13

Define osteopetrosis

Answer 13

Failure of normal bone resorption due to defective osteoclasts = thickened, dense bones that are prone to fracture

Question 14

Mutation that occurs in osteopetrosis and its result

Answer 14

(E.g carbonic anhydrase II) impairs ability of osteoclast to generate acidic env needed for bone resorption
Overgrowth of cortical bone fills marrow space = pancytopenia, extramedullary hematopoiesis
Can result in cranial nerve impingement, palsies due to narrowed foramina

Question 15

X-ray in osteopetrosis

Answer 15

Diffuse symmetric sclerosis (bone-in-bone, “stone bone”)

Question 16

Tx of osteopetrosis

Answer 16

Bone marrow transplant is potentially curative as osteoclasts are derived from monocytes

Question 17

Define osteomalacia + cause

Answer 17

Defective mineralization of osteoid (osteomalacia) or cartilaginous growth plates (rickets, only in children)
Commonly due to Vitamin D deficiency

Question 18

X-rays in osteomalacia/rickets

Answer 18

Osteomalacia: osteopenia, pseudofractures
Rickets: epiphyseal widening, metaphyseal cupping/fraying

Question 19

Presentation of rickets

Answer 19

Children have pathologic bow legs (genu varum), beadlike costochondral junctions (rachitic rosary), craniotabes (soft skull)

Question 20

Describe the pathophysiology of osteomalacia/rickets

Answer 20

Decreased vitamin D = Decreased serum calcium = increased PTH secretion and decreased serum phosphate
Hyperactivity of osteoblasts = increased ALP

Question 21

Define osteitis deformans

Answer 21

Aka Paget disease
Common, localized disorder of bone remodeling caused by increased osteoclast activity followed by increased osteoblast activity = poor quality bone
*Serum Ca, phosphate, PTH are normal
*Increased ALP

Question 22

Describe the findings of osteitis deformans

Answer 22

Mosaic pattern of woven and lamellar bone (osteocytes within lacunae in chaotic juxtapositions)
Long bone chalk-stick fractures
Hat size can be increased due to skull thickening
Hearing loss from skull deformity

Question 23

What can Paget disease result in

Answer 23

Increased blood flow from increased AV shunts may cause high-output heart failure
Increased risk of osteosarcoma

Question 24

Describe the stages of Paget disease

Answer 24

Early destructive (lytic): osteoclasts
Intermediate (mixed): osteoclasts/blasts
Late (sclerotic/blastic): Osteoblasts
May enter quiescent phase

Question 25

Tx of Paget

Answer 25

Bisphosphonates

Question 26

Define AVN of bone + where its most common and why

Answer 26

Infarction of bone and marrow, usually very painful
Most common site is femoral head (watershed zone) bc insufficiency of medial circumflex femoral artery

Question 27

Causes of AVN of bone

Answer 27

“CASTS Bend LEGS”
glucoCorticoids, chronic Alcohol use, Sickle cell disease, Trauma, SLE, “the Bends” (caisson/decompression disease), LEgg-Calve-Perthes, Gaucher, Slipped capital femoral epiphysis

Question 28

What lab findings are found in osteoporosis

Answer 28

Decreased bone mass
Lab values normal

Question 29

Lab findings (Ca, PO, ALP, PTH) in osteopetrosis

Answer 29

normal/decreased serum Ca
Dense, brittle bones (Ca decreased in severe, malignant disease)

Question 30

Lab findings (Ca, PO, ALP, PTH) in Paget

Answer 30

Increased ALP
Abnormal “mosaic” bone architecture

Question 31

Lab findings (Ca, PO, ALP, PTH) in osteitis fibrosa cystica (primary hyperparathyroidism)

Answer 31

Increased serum Ca, ALP, PTH
Decreased phosphate
“Brown tumors” due to fibrous replacement of bone, subperiosteal thinning
Idiopathic or parathyroid hyperplasia, adenoma, carcinoma

Question 32

Lab findings (Ca, PO, ALP, PTH) in osteitis fibrosa cystica (secondary hyperparathyroidism)

Answer 32

Increased phosphate, ALP, PTH
Decreased serum Ca
Often as compensation for CKD (decreased phosphate excretion and production of activated vitamin D)

Question 33

Lab findings (Ca, PO, ALP, PTH) in osteomalacia/rickets

Answer 33

Decreased serum Ca, phosphate
Increased ALP, PTH
Soft bones; vitamin D deficiency also causes 2° hyperparathyroidism

Question 34

Lab findings (Ca, PO, ALP, PTH) in hypervitaminosis D

Answer 34

Inc serum Ca, phosphate
Decreased PTH
Caused by oversupplementation or granulomatous disease (eg, sarcoidosis)

Question 35

Describe the type of tumour, location of osteochondroma

Answer 35

Most common benign tumour in males <25
Found in metaphysis of long bones

Question 36

Characteristics of osteochondroma

Answer 36

Lateral bony projection of growth plate (continuous with marrow space) covered by cartilaginous cap
Rarely transforms to chondrosarcoma

Question 37

Describe the type of tumour, location of osteoma

Answer 37

Benign, in middle age
Found in surface of facial bones

Question 38

Characteristics of osteoma

Answer 38

Associated w Gardner syndrome

Question 39

Describe the type of tumour, location of osteoid osteoma

Answer 39

In adult males < 25
Found in cortex of long bones

Question 40

Characteristics of osteoid osteoma

Answer 40

Presents as bone pain (worse at night) that is relieved by NSAIDs
Bony mass (< 2 cm) with radiolucent osteoid core

Question 41

Describe the type of tumour, location of chondroma

Answer 41

Benign tumour of cartilage found in medulla of small bones of hand and feet

Question 42

Describe the type of tumour, location of giant cell tumor

Answer 42

Benign tumour found in 20-40 year olds
In epiphysis of long bones (often knee region)

Question 43

Characteristics of giant cell tumour

Answer 43

Locally aggressive benign tumor
Neoplastic mononuclear cells that express RANKL and reactive multinucleated giant (osteoclastlike) cells. “Osteoclastoma”
“Soap bubble” appearance on x-ray