Osteonecrosis and Infection Flashcards
How does heterotrophic calcification appear?
Irregular, splotchy, and amorphous
What are the two types of heterotrophic calcification?
- Metastatic
- Dystrophic
heterotrophic calcification
What are some examples of metastatic calcification?
- Hypercalcemia
- Hyperphosphatemia
heterotrophic calcification
What are some examples of dystrophic calcification?
Occurs locally in diseased/damaged tissues ie. trauma, degenerative diseases, tumors
What is reactive bone formation?
Intramembranous bone formed in response to stress on bone or soft tissue
How does reactive bone formation work?
Stimulus lifts the periosteum resulting in intramembranous bone formation
What types of bone exhibit reactive bone formation?
Woven or lamellar
What are the types of periosteal reactions?
- Solid
- Laminated
- Spiculated
- Codman’s triangle
Besides periosteum, reactive bone formation can involve…
endosteum
What is a solid periosteal reaction?
The periosteum is lifted slowly and fills in completely
Slow growing, typically non-aggressive
What are some causes of solid periosteal reaction?
- Bone hemorrhage ie. fatigue fractures
- Benign bone tumors ie. osteoid osteoma
What is a laminated periosteal reaction?
Aggressive process where periosteum is lifted, stops, lifts again, and so on; bone is laid down during the rest phase
What is a spiculated periosteal reaction?
Aggressive process where periosteum is lifted rapidly and bone grows along the Sharpey fibers
How does spiculated periosteal reaction appear in radiographs?
“Hair on end” or “sunburst” appearance
What is Codman’s triangle?
Aggressive process extending beyond bone rapidly; periosteum is stripped from adjacent uninvolved bone
What is osteonecrosis?
Death of bone and bone marrow in the absence of infection
What is the cause of osteonecrosis?
What are some examples?
Loss of blood supply:
- Arterial rupture (trauma)
- Arterial compression (myoproliferative disorders)
- Arterial blockage (thromboembolic events)
How does osteonecrosis change name based on location?
- Epiphyseal: avascular necrosis
- Metaphyseal/diaphyseal: bone infarct
How is osteonecrosis histologically characterized?
Lack of cells: empty lacunae, dystrophic calcifications
How does osteonecrosis present radiographically?
- Necrotic zone may appear radio-opaque
- Radiolucent area surrounds necrotic bone
What is the acronym for osteonecrosis etiology?
PLASTIC RAGS:
Pancreatitis, pregnancy
Lupus
Aalcoholism
Steroids (corticosteroids)
Trauma
Idiopathic, infection
Caison disease, collagen vascular diseases, Cushing disease
Rheumatoid arthritis, radiation therapy
Amyloidosis
Gaucher disease
Sickle cell disease / thalassemia
What is osteomyelitis?
Inflammation of bone due to bacterial infection
60-80% of osteomyelitis are caused by which bacteria?
Staphylococcus aureus
What are two types of osteomyelitis?
- Acute pyogenic osteomyelitis
- Chronic osteomyelitis
What are the routes of spread of osteomyelitis?
- Hematogenous (blood)
- Direct inoculation (after open fracture)
- Direct spread from nearby infection
In the case of hematogenous osteomyelitis, bacteria spread from inside the bone to the subperiosteal space using the ___ and ___ canal systems
Haversian and Volkmann canal systems
The level and rate of tissue destruction or aggressiveness of osteomyelitis depends upon:
- Virulence of the bacteria
- Age of the patient
- Overall health of the patient
Who are high risk patients for osteomyelitis?
- Children
- Elderly
- Diabetics
- Immunocompromised
- IV drug abusers
- Homeless
- Post-surgical patients
What are some sources of hematogenous dissemination of osteomyelitis?
- Skin
- Dental sources
- Contaminated needles
- Other sites of infection
Which regions of bone are frequently affected by osteomyelitis?
Metaphyseal regions especially of lower extremity
What group of patients most commonly present with osteomyelitis?
Children 5-15 years of age
What is the nature of inflammation for acute pyogenic osteomyelitis?
Aggressive, virulent bacteria lift the periosteum and go through it to invade neighboring tissue relatively quickly
What is the nature of inflammation for chronic osteomyelitis?
Less virulent, will often lift periosteum, causing reactive bone formation
Can continue for years; may also progress through the periosteum after a long period of infection
osteomyelitis
What happens when bacteria escape the vasculature and proliferate?
- Bacteria lyse osteocytes
- Localized tissue necrosis
- Localized bone marrow edema
osteomyelitis
What is the result of bone marrow edema?
Increased medullary pressure due to mechanical compression of capillaries
How do osteoclasts act in response to osteomyelitis?
Activity increases in the area of the infection:
- Local osteolysis
- Regional osteopenia
osteomyelitis
What happens if bacteria break through the cortex into subperiosteal space and do not go through the periosteum?
- Necrotic debris creates localized pressure
- Lifts the periosteum, initiating reactive bone formation
osteomyelitis
What is periostitis?
Inflammation of the periosteum
osteomyelitis
Periostitis and increased pressure cause ___ contributing to ___
cause loss of blood supply to cortical bone contributing to necrosis
osteomyelitis
If the bacterial infection penetrates the periosteum, what may eventually be affected?
May penetrate joints, soft tissues, and skin
osteomyelitis
What is a sequestrum?
A piece of devascularized bone becomes separated from the remainder of the bone due to chronic osteomyelitis
osteomyelitis
What is an involucrum?
A layer of new bone growth outside existing sequestrum
osteomyelitis
What is a cloaca?
A gap in the cortex of a bone that allows the drainage of pus or other material from the bone into the adjacent tissues (due to chronic osteomyelitis)
osteomyelitis
What is a sinus?
Forms from the infected bone to the skin surface, draining pus through its tract