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What vitamin deficiency causes rickets in children and osteomalacia in adults?
vitamin D deficiency
Describe the levels of serum calcium, phosphate, vitamin D, and alkaline phosphatase in rickets and osteomalacia.
low serum calcium, phosphate, vitamin D
raised serum alkaline phosphatase
List 3/4 causes of vitamin D deficiency.
poor dietary intake
malabsorption from GI tract
renal disorders causing decreased synthesis of 1,25-dihydroxyvitamin D
rare inherited disorders
List 3/5 endocrine causes of secondary osteoporosis.
- most common
List 3 neoplasia causes of secondary osteoporosis.
List 3/4 general GI causes of secondary osteoporosis.
vitamin D or C deficiency
What hormone is involved in the pathogenesis of osteoporosis?
- thin bony trabecula
What disorder is associated with a brown tumor?
- giant cell tumor-like mass
- neo-vascularization, hemorrhage
How does chronic renal failure affect phosphate and calcium levels?
- secondary hyperparathyroidism due to decreased vitamin D metabolism in kidneys (inhibition of conversion of vitamin D to active metabolites by phosphate)
- diminished intestinal absorption of vitamin D
How does dialysis (for patients with chronic renal failure) cause renal osteodystrophy?
iron and aluminum from dialysate accumulate on bone and prevents bone deposition
What virus is associated with Paget disease?
- nucleocapsid antigens identified in osteoclasts
What gene mutation is associated with Paget disease?
- increases RANK/RANKL signalling, which leads to increased osteoclastic activity
List 2 cytokines involved in the pathogenesis of Paget disease.
- virus stimulates IL-6
- IL-6 and M-CSF activate osteoclasts, making them hyper-responsive to RANKL and vitamin D
List the 3 stages of Paget disease.
osteosclerotic stage: no osteoblastic or osteoclastic activity
- qualitatively weak bone = fractures
Describe the levels of serum alkaline phosphatase and urinary hydroxyproline in Paget disease.
increased serum alkaline phosphatase
increased urinary hydroxyproline
List 3 complications of Paget disease.
- high-output cardiac failure due to increased vascularization
- mix of woven bone and lamellar bone
List 2 tumors associated with Paget disease.
- osteosarcoma seen in elderly (normally 20-40 years of age)
List the 3 phases of fracture healing.
inflammatory phase (1 week)
reparative phase (2-3 weeks)
What is the name of the soft tissue callus formed towards the end of the inflammatory phase?
What proteins are responsible for post-fetal differentiation of mesenchymal cells into chondrocytes and osteoblasts?
What type of bone is formed during the early parts of the reparative stage of fracture healing?
What term is used to describe the mature lamellar bone that gradually replaces the woven bone of the primary callus?
List 3 systemic complications of fractures.
myoglobinuria (significant muscle injury)
List 2 routes of osteomyelitis. Which is more common?
hematogenous (seeding from systemic disease)
- more common
What is the most common bacteria that causes osteomyelitis?
- in 50% of cases, no pathogen is isolated
- receptors for bone matrix components, e.g. collagen
What type of bacteria should be implicated in osteomyelitis associated with genitourinary infection or IV drug abuse?
gram-negative rods (E. coli, Klebsiella, Pseudomonas)
Acute hematogenous osteomyelitis gender and general age groups (2)
young, growing children or adults > 50
List 4 common locations for acute hematogenous osteomyelitis.
femur, tibia, humerus
List 3 predisposing factors for acute hematogenous osteomyelitis.
What part of the bone is associated with acute hematogenous osteomyelitis? Explain why this part of the bone is ideal for bacterial growth.
- nutrient arteries terminate in venous sinusoids (ideal lakes for bacterial seeding) rather than forming anastamoses with veins through capillaries
- vascular loops and terminal branches have low oxygen tension and inhibited phagocytosis
What is the name of the necrotic bone that results from acute hematogenous osteomyelitis? What is the name of the new bone that develops around this necrosis?
- necrosis of nearby bony trabeculae due to loss of both endosteal and periosteal blood supply secondary to inflammatory swelling
List 3 predisposing factors for vertebral pyogenic osteomyelitis.
urinary tract infection
IV drug abuse
What part of the vertebrae is affected by vertebral pyogenic osteomyelitis?
begins in vertebral body then spreads through the vertebral end plate to involve the disc
- disc destruction more common in pyogenic than non-pyogenic infections of the spine
- may breach anterior cortex and ligamentous structures to form paravertebral soft tissue abscesses (retropharyngeal abscess, psoas abscess extending to groin and popliteal fossa)
- may spread posteriorly to involve the posterior arch and the neural canal
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