Acquired Bone Disorders - Gupta Flashcards by Jacob McMillan

What is osteoporosis?

Reduction in trabecular bone mass leading to porous bone –> increased risk of fracture

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What are the most common forms of osteoporosis?

Senile and postmenopausal

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What is the pathogenesis of osteoporosis?

For post-menopausal, all these things are a result of decreased Estrogen

There is also a decrease in OPG that causes the increased osteoclast activity (due to dec regulation)

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What does osteoporosis look like microscopically?

Normal bone (left) has thick trabeculae

Osteoporotic bone (right) has thinnned trabeculae

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Describe estrogen’s influence on bone? What cytokines are involved?

Estrogen increases osteoblast activity, decreases osteoclast activity

IL-1, IL-6, TNF modulate osteoclastogenesis (osteoclast differentiation, activation, life span, and function)

Estrogen inhibits secretions of these cytokines

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What is the most common fracture in people with osteoporosis?

Proximal femoral fractures –> associated with high mortality rate

Gupta notes contradict. Other sources say vertebral fractures more common

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What is osteomyelitis?

Infection of the bone, typically in children –> Most commonly bacterial

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What does acute osteomyelitis look like microscopically?

Neutrophils for dayz all up in the bone

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What are the symptoms and causes (3 patterns) of osteomyelitis?

Bone pain with signs of systemic infection

Caused by direct innoculation (bone trauma), contiguous spread (cellulitis), or hematogenous spread

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What are the bacteria (6) associated with osteomyelitis and populations most commonly seen in?

Staph aureus –> most common cause (90%)

Nisseria gonorrhoeae –> sexually active young adults

Pasteurella –> Dog/cat bites

Salmonella (encapuslated) –> Sickle cell disease

Pseudomonas –> DM and IV drug abusers, step on nail

TB –> usually invovles vertebrae (Pott’s disease)

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What does osteomyelitis look like on X-ray

Lytic focus (sequestrum) surrounded by sclerosis (involcrum) on X-ray

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What lab value will be very elevated in osteomyelitis?

ESR > 100mm/hr

Can also be seen in temporal arteritis and polymyalgia rheumatica

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What is osteonecrosis/avascular necrosis?

Necrosis of bone and bone marrow due to ischemia

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What are the causes of osteonecrosis?

1) Fracture/trauma
2) Long-term steroid use
3) Sickle cell –> dactylitis
4) Alcohol abuse
5) Decompression sickness –> N2 emboli lodge in bones (Caisson disease)

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What does osteonecrosis look like grossly?

Wedge shaped pale area of necrosis in bone

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What does osteonecrosis look like microscopically in sickle cell?

Diffusely congested, hemorrhagic marrow during sickle cell crisis

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What is Pagets disease of bone?

Imbalance between osteoclast and osteoblast activity –> osteoclasts are overactive

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What is the bone localization of Pagets disease?

Localizes to one or more bones –> does not involve entire skeleton

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What is the epidemiology of Pagets disease?

Usually pts in their 60s

If pt >40 and has isolated elevated AlkPhos, suspect Pagets

Familial link to chromosome 18

What are the three stages of Pagets disease?

1) Osteoclastic
2) Mixed osteoblastic-osteoclastic
3) Osteoblastic

What are the clinical features of Pagets disease?

1) Bone pain –> microfractures
2) Increased hat size –> skull is common site
3) Hearing loss –> Impingement on cranial nerve
4) Lion-like facies –> involvement of facial bones
5) Isolated elevated AlkPhos

What is seen on biopsy with Pagets disease?

Mosaic pattern of lamellar bone –> lots of pieces but none are fused

What is osteomalacia(adults)/Rickets(kids)?

Inadequate mineralization of bone due to low VitD (“kids need the D” - Jared Fogle) –> leads to weak bones and fracture

What lab findings are there in osteomalacia/Rickets?

1) Decreased serum calcium
2) Decreased serum phosphate
3) Increased PTH
4) Increased AlkPhos

What is the microscopic appearance of osteomalcia?

Surfaces of bony trabeculae (black) are covered by a layer of unmineralized osteoid (dark pink) --\> van Kossa stain turns calcified tissue black

What are the clinical features of Rickets?

1) Pigeon-breast deformity --\> inward bending ribs with anteriorly displaced sternum 2) Frontal bossing --\> osteoid deposition on the skull 3) Rachitic rosary --\> osteoid deposition at costochondral joints 4) Bowing of the legs

What is hyperparathyroidism?

Overactivity of parathyroid glands producing excess PTH

What are the causes of primary and secondary hyperparathyroidism?

Primary --\> Hyperplasia or tumor of parathyroid glands Secondary --\> Prolonged hypocalcemia leading to lots of PTH

How does hyperparathyroidism effect bone?

Excess PTH detected by osteoblasts --\> activate osteoclasts and bone is resorbed causing cyst-like **brown** tumors in bone

What does hyperparathyroidism look like microscopically in bone?

Brown tumors show fibroblasts mixed with osteoclasts and numerous activated osteoclasts (large, dark pink multinuclated cells) at the edge of trabecula

What is the bone disease associated with hyperparathyroidism called?

Osteitis fibrosa cystica - von Recklinghausen disease of bone

What is renal osteodystrophy?

Term to collectively describe skeletal changes associated with chronic renal disease – kidney fails to convert Vitamin D to active form

What is the pathogenesis of renal osteodystrophy?

Decreased VitD leads to reduced Ca2+ absoprtion from intestines --\> hypocalcemia causes increased PTH and increased bone resportion

What is a bone fracture (don't fuck this up)?

A break in the continuity of bone

What are the types of fracture?

1) Closed (simple) --\> doesn't penetrate skin 2) Open (compound) --\> penetrates skin 3) Displaced --\> separated in non-anatomic position 4) Pathologic --\> bones fracture due to pathologic process (osteoporosis) 5) Spiral --\> fracture from torque (child abuse)

If a patient has a compound fracture, what should you do before closing the wound?

Washout and give antibiotics to prevent infection

If a patient has a displaced fracture, what must you do before it can heal?

Must reduce the fracture back to anatomical position

What is a stress (hairline) fracture?

Fracture caused by repeated stress on a bone --\> often weight bearing bones

What typically causes a scaphoid fracture?

Falling on an outstretched hand --\> pain in the anatomical snuffbox

What is the necessary treatment in scaphoid fracture?

Splint the patient to prevent avascular necrosis

What causes a basillar skull fracture and how does it present?

Secondary to trauma Presents as periorbital ecchymoses, mastoid ecchymoses, CSF leaking thorugh ears or nose (metallic, salty taste)

What fractures in children are suspected for non-accidental trauma?

1) Rib fracture 2) Spiral fractures (except Toddler's fracture of distal tibia) 3) Multiple fractures of different ages 4) Shaken baby syndrome causing subdural hematoma and retinal hemorrhage

What happens immediately after a bone fracture?

Hematoma fills fracture gap and surroudning area of bone-injury to provide framework --\> allows platelets and inflammatory cells to do their part

One week after a fracture, what is happening?

1) New osteoprogenitor cells 2) Granulation tissue containing vessels and fibroblasts 3) Hematoma is removed

What happens 2-3 weeks after a fracture?

Early callus formation --\> cannot support weight

What is the final stage of healing after a fracture?

Bony callus mineralizes so controlled weight bearing can be tolerated

What are some complications of a fracture?

1) Fat emboli 2) DVT and PE 3) Compartment syndrome --\> Five **P**s: Pain, Pallor, Paresthesias, Pulselessness, Paralysis