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Musculoskeletal Physiopathology > Osteonecrosis and Infection > Flashcards

Osteonecrosis and Infection Flashcards

1
Q

How does heterotrophic calcification appear?

A

Irregular, splotchy, and amorphous

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2
Q

What are the two types of heterotrophic calcification?

A
  • Metastatic
  • Dystrophic
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3
Q

heterotrophic calcification

What are some examples of metastatic calcification?

A
  • Hypercalcemia
  • Hyperphosphatemia
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4
Q

heterotrophic calcification

What are some examples of dystrophic calcification?

A

Occurs locally in diseased/damaged tissues ie. trauma, degenerative diseases, tumors

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5
Q

What is reactive bone formation?

A

Intramembranous bone formed in response to stress on bone or soft tissue

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6
Q

How does reactive bone formation work?

A

Stimulus lifts the periosteum resulting in intramembranous bone formation

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7
Q

What types of bone exhibit reactive bone formation?

A

Woven or lamellar (cortical, trabecular)

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8
Q

What are the types of periosteal reactions?

A
  • Solid
  • Laminated
  • Spiculated
  • Codman’s triangle
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9
Q

Besides periosteum, reactive bone formation can involve…

A

endosteum

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10
Q

What is a solid periosteal reaction?

A

The periosteum is lifted slowly and fills in completely
Slow growing, typically non-aggressive

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11
Q

What are some causes of solid periosteal reaction?

A
  • Bone hemorrhage ie. fatigue fractures
  • Benign bone tumors ie. osteoid osteoma
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12
Q

What is a laminated periosteal reaction?

A

Aggressive process where periosteum is lifted, stops, lifts again, and so on; bone is laid down during the rest phase

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13
Q

What is a spiculated periosteal reaction?

A

Aggressive process where periosteum is lifted rapidly and bone grows along the Sharpey fibers

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14
Q

How does spiculated periosteal reaction appear in radiographs?

A

“Hair on end” or “sunburst” appearance

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15
Q

What is Codman’s triangle?

A

Aggressive process extending beyond bone rapidly; periosteum is stripped from adjacent uninvolved bone

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16
Q

What is osteonecrosis?

A

Death of bone and bone marrow in the absence of infection

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17
Q

What is the general cause of osteonecrosis?
What are some specific examples?

A

Loss of blood supply:

  • Arterial rupture (trauma)
  • Arterial compression (myoproliferative disorders)
  • Arterial blockage (thromboembolic events)
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18
Q

How does osteonecrosis change name based on location?

A
  • Epiphyseal: avascular necrosis
  • Metaphyseal/diaphyseal: bone infarct
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19
Q

How is osteonecrosis histologically characterized?

A

Lack of cells: empty lacunae, dystrophic calcifications

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20
Q

How does osteonecrosis present radiographically?

A
  • Necrotic zone may appear radio-opaque
  • Radiolucent area surrounds necrotic bone
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21
Q

What is the acronym for osteonecrosis etiology?

A

PLASTIC RAGS:
Pancreatitis, pregnancy
Lupus
Alcoholism
Steroids (corticosteroids)
Trauma
Idiopathic, infection
Caison disease, collagen vascular diseases, Cushing disease

Rheumatoid arthritis, radiation therapy
Amyloidosis
Gaucher disease
Sickle cell disease / thalassemia

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22
Q

What is osteomyelitis?

A

Inflammation of bone due to bacterial infection

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23
Q

60-80% of osteomyelitis is caused by which bacteria?

A

Staphylococcus aureus

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24
Q

What are two types of osteomyelitis?

A
  • Acute pyogenic osteomyelitis
  • Chronic osteomyelitis
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25
Q

What are the routes of spread of osteomyelitis?

A
  1. Hematogenous (blood)
  2. Direct inoculation (after open fracture)
  3. Direct spread from nearby infection
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26
Q

In the case of hematogenous osteomyelitis, bacteria spread from inside the bone to the subperiosteal space using the ___ and ___ canal systems

A

Haversian and Volkmann canal systems

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27
Q

The level and rate of tissue destruction or aggressiveness of osteomyelitis depends upon:

A
  • Virulence of the bacteria
  • Age of the patient
  • Overall health of the patient
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28
Q

Who are high risk patients for osteomyelitis?

A
  • Children
  • Elderly
  • Diabetics
  • Immunocompromised
  • IV drug abusers
  • Homeless
  • Post-surgical patients
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29
Q

What are some sources of hematogenous dissemination of osteomyelitis?

A
  • Skin
  • Dental sources
  • Contaminated needles
  • Other sites of infection
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30
Q

Which regions of bone are frequently affected by osteomyelitis?

A

Metaphyseal regions especially of lower extremity

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31
Q

What age group of patients most commonly presents with osteomyelitis?

A

Children 5-15 years of age

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32
Q

What is the nature of inflammation for acute pyogenic osteomyelitis?

A

Aggressive, virulent bacteria lift the periosteum and go through it to invade neighboring tissue relatively quickly

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33
Q

What is the nature of inflammation for chronic osteomyelitis?

A

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

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34
Q

osteomyelitis

What happens when bacteria escape the vasculature and proliferate to bone?

A
  • Bacteria lyse osteocytes
  • Localized tissue necrosis
  • Localized bone marrow edema
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35
Q

osteomyelitis

What is the result of bone marrow edema?

A

Increased medullary pressure due to mechanical compression of capillaries

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36
Q

How do osteoclasts act in response to osteomyelitis?

A

Activity increases in the area of the infection:

  • Local osteolysis
  • Regional osteopenia
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37
Q

osteomyelitis

What happens if bacteria break through the cortex into subperiosteal space and do not go through the periosteum?

A
  • Necrotic debris creates localized pressure
  • Lifts the periosteum, initiating reactive bone formation
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38
Q

osteomyelitis

What is periostitis?

A

Inflammation of the periosteum

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39
Q

osteomyelitis

Periostitis and increased pressure cause ___ contributing to ___

A

cause loss of blood supply to cortical bone contributing to necrosis

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40
Q

osteomyelitis

If the bacterial infection penetrates the periosteum, what may eventually be affected?

A

May penetrate joints, soft tissues, and skin

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41
Q

osteomyelitis

What is a sequestrum?

A

A piece of devascularized bone becomes separated from the remainder of the bone due to chronic osteomyelitis

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42
Q

osteomyelitis

What is an involucrum?

A

A layer of new bone growth outside existing sequestrum

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43
Q

osteomyelitis

What is a cloaca?

A

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)

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44
Q

osteomyelitis

What is a sinus?

A

Forms from the infected bone to the skin surface, draining pus through its tract

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45
Q

What are some ways reactive bone formation, due to chronic osteomyelitis, may change the architecture of the bone over time?

A
  • Enlargement
  • Sequestrum
  • Involucrum
46
Q

What are some physical characteristics of chronic osteomyelitis?

A
  • Reactive bone formation changing architecture
  • Cloaca and possibly sinus
  • Multiple lytic lesions in bone, may result in porous appearance
  • Can destroy multiple bones and multiple tissues over time
47
Q

If multiple bones and multiple tissues are involved, ___ must be on your differential diagnosis until proven otherwise

A

infection

48
Q

Osteomyelitis (acute pyogenic) presents with which cardinal signs?

A
  • Rubor (redness)
  • Dolor (throbbing pain worsening rapidly)
  • Calor (rapid onset/increasing high fever)
  • Tumor (swelling)
49
Q

___% of bone infections become chronic

A

10%

50
Q

What is a Marjolin ulcer?

A

Squamous cell carcinoma (rare) of the bone (infection)

51
Q

When are changes in bone due to infection radiographically visible in the extremities?
What about in the spine?

A

Extremities: 7-10 days
Spine: 21 days

52
Q

What are some radiographic findings in osteomyelitis?

A
  • Loss of cortical definition
  • Loss of trabecular patterning
  • Aggressive periosteal reaction
53
Q

What is spondylodiscitis?

A

Vertebral osteomyelitis

54
Q

What are some risk factors for spondylodiscitis?

A
  • Hematogenous spread from other sites
  • Intravenous drug use
  • Upper urinary tract infections
  • Urological procedures
  • Discitis
55
Q

What are three possible consequences of spondylodiscitis?

A
  1. Vertebral collapse and paravertebral abscess
  2. Spinal epidural abscesses with cord compression by abscess or displaced fragments of infected bone
  3. Compression fractures of vertebral body
56
Q

Spondylodiscitis can lead to compression fractures of vertebral bodies
What would be a consequence of this?

A

Neurological deficits

57
Q

Where does spondylodiscitis tend to occur?

A

Thoraco-lumbar region, but can be anywhere

58
Q

What are the radiographic characteristics of spondylodiscitis?

A
  • Decreased/obliterated disc space
  • Loss of vertebral endplates
59
Q

What are some possible laboratory findings in spondylodiscitis?

A
  • Leukocytosis
  • Elevated ESR
  • Increased C-reactive protein
  • Blood culture
60
Q

How might acute infections of spondylodiscitis be treated?

A
  • IV antibiotics, usually for at least 6 weeks
  • Possible surgery to drain and decompress infected area/abscesses
61
Q

How might chronic or more severe infections of spondylodiscitis be treated?

A
  • More surgical intervention for debridement of necrotic bone and drainage of abscesses
  • Amputation
  • Life long or symptomatic antibiotic regimens

(very difficult to treat)

62
Q

What is a Brodie abscess?
Where are they generally seen/often found?

A

Subacute metaphyseal infection of bone
Generally seen in children, often found in tibia, femur, fibula, radius

63
Q

How does bone react to a Brodie abscess?

A
  • Osteolytic lesion gets walled off
  • Reactive bone from periosteum and endosteum forms around lesion
  • May result in sterilization of the lesion
64
Q

What is the etiology of tuberculosis?

A

Mycobacterium tuberculosis

65
Q

Where does tuberculosis of bone originate from?

A

Infection in other areas:

  • Lungs or lymph nodes
  • Bovid strain infection may originate in the guts or tonsils
66
Q

How does tuberculosis spread from other areas of the body to bone?

A

Hematogenous spread; rarely, direct seeding or implantation

67
Q

Which age group is usually affected by tuberculosis?

A

Individuals 1-30 years of age

68
Q

Which bones are most affected by tuberculosis?

A

The spine: tuberculosis spondylitis / Pott disease (lungs to spine)

69
Q

What is the pattern and morphology of inflammation associated with tuberculosis infection?

A

Chronic granulomatous inflammation

70
Q

What pattern of necrosis is associated with tuberculosis infection?

A

Caseous necrosis

71
Q

In tuberculosis, what happens with the mycobacterium that allows it to spread?

A

Mycobacterium exit the vasculature

72
Q

Which feature of tuberculosis produces caseous necrosis?

A

Granulomas

73
Q

In tuberculosis, caseous necrosis leads to gradual resorption of ___

A

bony trabeculae

74
Q

With tuberculosis, what reactive bone formation occurs?

A

Little to no reactive bone formation

75
Q

What happens if tuberculosis infection ruptures into soft tissues?

A

Cold abscesses (abscesses lacking acute inflammation) occur in spinal ligaments

76
Q

How does resorption of bony trabeculae involved in tuberculosis affect the spine?

A
  • Bone is destroyed
  • Weakened vertebral bone collapses under continued mechanical stress (pronounced collapse)
  • Rupture and extrusion of the intervertebral disc
77
Q

Can mycobacterium of tuberculosis invade intervertebral discs directly?

A

No

78
Q

Describe the clinical onset of tuberculosis

A

Insidious onset: initial pain is usually mild, comes with stiffness

79
Q

How does tuberculosis present upon static and motion palpation?

A

Focal tenderness, decreased ROM

80
Q

Does spinal pain due to tuberculosis have neurological involvement?

A

May or may not

81
Q

What is an example of a cold abscess found in patients with tuberculosis?

A

Psoas abscess

82
Q

What is Gibbus deformity?

A

Sharply angled kyphosis in thoracic spine due to vertebral collapse as a result of tuberculosis

83
Q

How might tuberculosis lead to paraplegia?

A

Results from vascular insufficiency of spinal nerves

84
Q

What is the trend of reported syphilis infections?

A

All syphilis types increasing over time, a reemerging public health concern

85
Q

What is the etiology of syphilis?

A

Treponema pallidum

86
Q

What are the two types of syphilis?

A
  • Acquired
  • Congenital
87
Q

How is acquired syphilis transmitted?

A

STD/venereal

88
Q

How is congenital syphilis transmitted?

A

Transplacental contraction

89
Q

When does bone involvement occur in syphilis?

A

2-5 years after exposure

90
Q

What portion of syphilis patients will develop bone lesions?

A

<10%

91
Q

Which bones are most commonly impacted by syphilis?

A

Tibia, nose, palate, skull

92
Q

What are saber shins?

A

Anterior bowing of the shins due to congenital syphilis or rickets

93
Q

Why do syphilis patients present with saber shins?

A

Periostitis leads to reactive bone formation

94
Q

What sort of osseous necrosis can occur in patients with syphilis?

A
  • Lysis and collapse of nasal and palatal bones
  • Saddle nose: destruction and eventually collapse of nasal septum
95
Q

Where are gummas most common?

A

Skin, bones, and joints

96
Q

What are gummas?

A

Granulomatous lesions with central area of coagulative necrosis, epithelioid macrophages, and giant cells surrounded by fibrous tissue

97
Q

Bone adjacent gummas is gradually replaced by ___

A

fibrous marrow

98
Q

How is the cortex of the bone affected by gummas?

A

Cortex is perforated

99
Q

How does bone with gummas eventually appear?

A

Surface shows thickened periosteal response and perforated, ulcerations with wavy margins

100
Q

Congenital syphilis involves the same lesions as adult infection
What are they?

A
  • Saddle nose
  • Saber shin
  • Gummas
  • Bone erosion and destruction
  • Neurological symptoms
101
Q

What are Hutchinson teeth?

A

Altered dental development associated with congenital syphilis; teeth have grooves along their edges

102
Q

How does bone respond to congenital syphilis spirochetes lodging into growth plates?

A
  • Vascularized tissues under the growth plate are destroyed and replaced by granulation tissue
  • Bone formation and remodeling are decreased or absent
103
Q

How do growth plate infections due to congenital syphilis appear on radiographs?

A

A widened growth plate or broad radiolucent metaphyseal bands

104
Q

What is pseudoparalysis of Parrot?

A

Dislocated epiphysis, functionless limb associated with congenital syphilis

105
Q

With congenital syphilis, the medullary cavity is filled with ___ replacing normal marrow

A

lymphocytes, plasma cells, and spirochetes

106
Q

With congenital syphilis, as bones grow, they become ___

A

shortened and deformed

107
Q

With congenital syphilis, a periosteal reaction stimulates ___

A

thickening cortex

108
Q

New bone formation that forms a sheath around an area of necrotic bone is called ___

A

involucrum

109
Q

A hyperkyphosis in the thoracolumbar spine due to tuberculosis infection may also be called ___

A

Gibbus deformity

110
Q

What clinical presentation is specific to congenital syphilis?

A

Hutchinson teeth

Musculoskeletal Physiopathology (31 decks)

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