Goljan's MSK Flashcards
What causes osteogenesis imperfecta?
Defect in synthesis of type I collagen (AD)
What is the mechanism of blue sclera in OI?
Reflection of the underlying choroidal veins through thin sclera
What causes achondroplasia?
AD mutation in the FGFR3 gene
How does achondroplasia present?
Normal head/axial skeleton, short arms/legs, impaired proliferation of cartilage at growth plate
What is the pathogenesis of osteopetrosis?
Deficiency of osteoclasts (AR); “too much bone”
What are the clinical findings in osteopetrosis?
Pathologic fractures, visual/hearing loss, anemia
How does osteomyelitis spread?
Usually spreads hematogenously to bone
What is the most common site of osteomyelitis?
Metaphysis
What is the most common pathogen causing osteomyelitis?
S. aureus
What is the most common pathogen causing osteomyelitis in sickle cell disease?
S. paratyphi
What is Pott disease?
Tuberculous osteomyelitis involving the vertebral column
What pathogen causes osteomyelitis following puncture of foot through rubber footwear?
P. aeruginosa
What is sequestra?
Devitalized bone
What is involucrum?
Reactive bone formation in periosteum
What is a late complication of draining sinus tracts?
Danger of SCC at sinus drainage orifice
What is the most common metabolic abnormality of bone?
Osteoporosis
What defines osteoporosis?
Loss of both mineralized bone and organic bone matrix (osteoid)
What is primary osteoporosis?
Idiopathic; most common in children and young adults
Who is prone to type I osteoporosis?
Postmenopausal women
What is type II osteoporosis?
Senile type; occurs in men and women
What are some causes of secondary osteoporosis?
↑ cortisol, heparin, hypogonadism, malnutrition, space travel
What is the role of estrogen in maintaining bone mass?
Estrogen normally inhibits production of osteoclasts and enhances the activity of osteoblasts
How does decreased estrogen affect bone mass?
↓EGN: ↑IL-1, IL-6, TNF → ↑osteoclastogenesis
What cytokines mediate osteoclastogenesis?
IL-1, IL-6, TNF
What are the effects of IL-1, IL-6, and TNF on bone?
↑ expression of RANK, RANKL genes, ↓ expression of osteoprotegerin (OPG)
What is the mechanism of bone loss in postmenopausal bone mass?
↓EGN: osteoclast activity > osteoblast activity
Which fractures occur most commonly in postmenopausal osteoporosis?
Vertebral compression fractures, Colles fracture
How is osteoporosis diagnosed?
Dual photon absorptiometry
How can osteoporosis be prevented?
Weight-bearing exercises, supplementation of calcium + vit D, smoking cessation
How is osteoporosis treated?
Bisphosphonates (first-line), Estrogen replacement in women
What is avascular necrosis?
Death of bone cells from blood supply interruption
What is the most common site of avascular necrosis?
Femoral head
What is the most common cause of avascular necrosis?
Long-term use of corticosteroids
What is the mechanism of avascular necrosis in the femoral head?
Subcapsular fracture disrupts blood supply (retinacular arteries from medial circumflex femoral artery)
Which wrist bone is most commonly fractured?
Scaphoid bone; susceptible to avascular necrosis
What is the most sensitive early test for avascular necrosis?
MRI
What is osteochondrosis?
Avascular necrosis of ossification centers in children
What is Legg-Calvè-Perthes disease?
Avascular necrosis of the femoral head ossification center; boys > girls
What is osteochondritis dissecans?
Variant of osteochondrosis limited to articular epiphysis
What causes osteochondritis dissecans?
Trauma is primary insult; ischemia is secondary injury
What is the most common site of osteochondritis dissecans?
Lateral surface of medial femoral condyle
What occurs in osteochondritis dissecans of the knee?
Piece of cartilage along with a thin layer of bone detaches
What is a late complication of osteochondritis dissecans?
Osteoarthritis
What is Osgood-Schlatter disease?
Painful swelling of tibial tuberosity at patellar tendon insertion; affects physically active boys
What is a typical finding associated with Osgood-Schlatter disease?
Permanent knobby-appearing knees
What population is typically affected by Paget disease?
Primarily occurs in men >50 years of age
What is the etiology of Paget disease?
Unknown; possible paramyxovirus infection of osteoclasts
What bones are targeted in Paget disease?
Pelvis, skull, femur
What is the pathogenesis of Paget disease?
Osteoclastic phase followed by an osteoblastic phase
What are are the clinical findings in Paget disease?
↑ALP in osteoblastic phase, weak thick vascular bone
How does Paget disease typically present?
pain, ↑hat size
What are some complications of Paget disease?
Fractures, osteogenic sarcoma, high output heart failure
What causes fibrous dysplasia?
Defect in osteoblastic differentiation/maturation
What occurs in fibrous dysplasia?
Medullary bone replaced by fibrous tissue with cyst formation
What is the most common site of fibrous dysplasia?
Ribs
What are the features of [McCune]-Albright syndrome?
Polyostotic bone involvement, cafe au lait spots, precocious puberty
What are the complications of fibrous dysplasia?
Pathologic fracture, osteogenic sarcoma, fibrosarcoma
What is the most common bone malignancy?
Metastasis (breast cancer is most common source)
What is the most common benign bone tumor?
Osteochondroma
What are the characteristics of monosodium urate crystals?
Monoclinic (needle-shaped), Negative birefringence (yellow when parallel to slow ray)
What are the characteristics of calcium pyrophosphate crystals?
Monoclinic-like (needle-like) or triclinic (rhomboid), Positive birefringence (blue when parallel to slow ray)
What does a mucin clot test for?
Joint viscosity; hyaluronic acid is the key lubricant in synovial fluid
What joint disorders are classified as group I?
Noninflammatory: osteoarthritis, neuropathic joint
What joint disorders are classified as group II?
Inflammatory: rheumatoid arthritis, gout
What joint disorders are classified as group III?
Septic: lyme disease, dissemminated gonococcemia
What joint disorders are classified as group IV?
Hemorrhagic: trauma, hemophilia
Morning stiffness is a characteristic finding in which diseases?
Rheumatoid arthritis, SLE, polymyalgia rheumatica
What are some examples of joint effusion?
Blood, exudate
What is implied by a hot joint?
Acute inflammation; septic arthritis
What is joint crepitus?
Crackling feeling when joint moves; characteristic of osteoarthritis