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Infectious Disease 2 > Osteomyelitis > Flashcards

Osteomyelitis Flashcards

1
Q

Osteomyelitis

- Define

A
  • Inflammation of bone that is almost always due to infection
  • MC bacterial but can be viral or fungal as well
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2
Q

Three ways to classify osteomyelitis

A
  1. timing
  2. mechanism of injury
  3. type of host response
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3
Q

Osteomyelitis classification

- timing

A
  • Acute <2 weeks
  • Subacute 2-6 weeks
  • Chronic > 6 weeks
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4
Q

Osteomyelitis classification

- Mech. of injury

A
  • Exogenous: originates from outside the body

- Hematogenous: originates from body itself

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5
Q

Osteomyelitis classification

- host response

A
  • Pyogenic: produces pus from infecting org

- Non-pyogenic: no abscess or pus production

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6
Q

Keys to clinical success

A
  • Early dx

- Appropriate surgical and antimicrobial treatment (may require multidisciplinary approach: ortho, ID, plastics)

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7
Q

Three types of osteomyelitis studied

A
  • acute hematogenous
  • subacute hematogenous
  • chronic
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8
Q

What is MC type of osteomyelitis

A

Acute Hematogenous

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9
Q

Acute Hematogenous Osteomyelitis

- ages affected

A
  • MC <2 and 8-12
  • MC in males
  • can occur in adults
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10
Q

Acute Hematogenous Osteomyelitis

- areas of bone effected

A
  • children: long bone metaphysis d/t bacteremia MC

- adults: vertebrae MC, also long bones, pelvis, clavicle

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11
Q

Acute Hematogenous Osteomyelitis

- was is bacterial seeding associated with?

A
  • localized trauma
  • chronic illness
  • malnutrition
  • inadequate immune system
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12
Q

Acute Hematogenous Osteomyelitis

- overview of patho in children

A
  • Metaphysis is rapidly growing and has a lot of vasculature
  • Bacterial seeding → inflammatory rxn, causing localized ischemic necrosis of bone and subsequent bone abscess formation
  • Abscess enlarges, causing intramedullary pressure, cortical ischemia and destruction.
  • The purulent infectious material can escape the cortex and enter the subperiosteal space → subperiosteal abscess
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13
Q

Acute Hematogenous Osteomyelitis

- what happens if untreated?

A

extensive sequestra formation and chronic osteomyelitis

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14
Q

Acute Hematogenous Osteomyelitis

- two major complications

A
  1. Involcrum: thick sheath of periosteal new bone surrounding a sequestrum
  2. Sequestrum:
    - Devascularization of a portion of bone with necrosis and resorption of surrounding bone leaving a “floating” piece
    - Acts as a reservoir for infection
    - Avascular = not penetrated by abx, usually requires excision
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15
Q

Acute Hematogenous Osteomyelitis

- pathophys for children <2 yo

A
  • Blood vessels cross the physis, allowing epiphysis involvement
  • Can result in limb shortening or angular deformities
  • Contiguous joint involvement can occur, more likely if involves intra-articular physis: MC is hip, also proximal humerus, radial neck, distal fibula. Can results in septic arthritis
  • Metaphysis has relatively fewer phagocytic cells than physis or diaphysis = more infection potential
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16
Q

Acute Hematogenous Osteomyelitis

- pathophys children >2 yo

A
  • Physis acts like a barrier to spread from metaphyseal abscess
    o Once physis is closed, acute hematogenous osteomyelitis is much less common
    o Once physis is closed, infection can extend directly from metaphysis into epiphysis and involve the joint (why septic arthritis from acute hematogenous osteomyelitis is seen only in infants and adults)
  • The metaphyseal cortex is thicker so diaphysis is at more risk
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17
Q

Acute Hematogenous Osteomyelitis

- microbiology

A
  • Older children and adults: Staphylococcus aureus
  • Infants: S. aureus. Also Group B Streptococcusand gram negative coliforms
  • Premature neonates: S. aureus and gram neg orgs
  • Incidence of Hemophilus influenza decrease d/t immunizations, MC in children 6 months – 4 years
  • Adult vertebral infection: gram negative bacteria
  • IV drug users: Pseudomonas
  • Sickle cell: Salmonella, tends to be diaphyseal
  • Chronically ill, long term IV therapy: fungal infections
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18
Q

Acute Hematogenous Osteomyelitis

- Hx and PE

A
  • Fever, malaise
  • Pain, localized tenderness
  • Swelling
  • Compartment syndrome in children
19
Q

Acute Hematogenous Osteomyelitis

- Labs for dx

A
  • CBC: often have NL WBC
  • CRP: usu elevated. Repeat 2-3 days after abx
  • ESR no longer used, replaced by CRP
  • Abscess or bone aspiration for C&S
20
Q

Acute Hematogenous Osteomyelitis

- Imaging for dx

A
  • Plain films: usu not visible for 10-12 days
  • Technetium 99m bone scan: can confirm dx 24-48 hours after onset in 90-95% of cases
  • MRI: early inflammatory changes in bone marrow or soft tissue involvement
21
Q

Acute Hematogenous Osteomyelitis

- Tx overview

A
  • No abscess, abx may be sufficient: empirical coverage, if no response in 24-48 hours, then occult abscesses must be sought, surgical drainage considered
  • Often abx and surgery required
22
Q

Acute Hematogenous Osteomyelitis

- Nade’s Principles of treatment

A
  • Abx will be appropriate before pus formation
  • Abx will not sterilize avascular tissue or abscesses, will require surgical debridement (refer to ortho)
  • If removal is effective, ax will prevent reformation so primary wound closure should be safe
  • Surgery should not further damage already ischemic bone and soft tissue
    Abx should be considered after sx
23
Q

Acute Hematogenous Osteomyelitis
Surgery
- 2 indications
- 2 objectives

A

Indications
• Presence of abscess that requires drainage
• Failure of pt to improve despite IV abx

Two objectives
• Drain abscess cavity
• Remove nonviable or necrotic tissue

24
Q

Subacute Hematogenous Osteomyelitis

- overview

A

More insidious onset; lacks severity of sx compared to acute

25
Q

Subacute Hematogenous Osteomyelitis

- why is dx often delayed?

A

Often 2+ weeks, indolent course bc:

  • Increased host resistance
  • Decreased bacterial virulence
  • Admin of abx before onset of sx
26
Q

Subacute Hematogenous Osteomyelitis

- Hx and PE

A
  • Minimal systemic s/sx
  • Mild temp elevation
  • Mild-mod pain
27
Q

Subacute Hematogenous Osteomyelitis

- Dx

A

Labs

  • CBC: WBC general NL
  • ESR: elevated in only 50% of pts
  • Blood cultures: gen negative

Plain film: generally positive

28
Q

Subacute Hematogenous Osteomyelitis

- organisms

A

Staph aureus and Staph epidermidis

29
Q

Subacute Hematogenous Osteomyelitis

- Brodie abscess describe

A
  • Localized form of subacute osteomyelitis
  • S. aureus positive culture in 50%
  • MC in long bones of LE
  • MC complaint: intermittent pain of long duration and tenderness over affected area
30
Q

Subacute Hematogenous Osteomyelitis

- Brodie abscess on plain film

A

lytic lesion with a rim of sclerotic bone

31
Q

Subacute Hematogenous Osteomyelitis

- Brodie abscess dx

A
  • Aggressive lesions require open bx with curettage

- Simple abscess in epiphysis or metaphysis: bx not recommended. Just IV abx X 48 hours + 6 weeks oral abx

32
Q

Subacute Hematogenous Osteomyelitis

- Brodie abscess tx

A
  • close wound loosely over drain (if open bx with curettage)

- abx

33
Q

Subacute Hematogenous Osteomyelitis

- Brodie abscess classification

A

Gledhill classification

34
Q

Chronic osteomyelitis

- hallmark sx

A
  • Infected dead bone with compromised soft tissue envelope
  • Infected focci in bone are surrounded by sclerotic, relatively avascular bone with thickened periosteum and scarred muscle and subcutaneous tissue
35
Q

Chronic osteomyelitis

- Types

A
  • Medullary: in the medulla
  • Superficial: cortical surface infected d/t coverage defect
  • Localized: cortical sequestrum, can be excised w/o compromising stability
  • Diffuse: features of all other types, mechanical instability before or after debridement
36
Q

Chronic osteomyelitis

- Hx and PE

A
  • Skin/soft tissue integrity
  • Tenderness
  • Bone stability
  • Neurovascular status of limb
  • Presence of sinus track
37
Q

Chronic osteomyelitis

- lab dx

A
  • ESR and CRP
  • WBC elevated 35%
  • Bx for histological and microbiological eval: staph. aureus, anaerobes, gram-neg bacilli
38
Q

Chronic osteomyelitis

- Imaging overview

A
  • Plain film
  • Sinography (nuclear med)
  • Isotropic bone scanning (more useful in acute vs. chronic)
  • Gallium scan
  • CT
  • MRI
39
Q

Chronic osteomyelitis

- Plain film

A

** takes 10-12 days to show up
• Cortical destruction
• Periosteal reaction
• Sequestra

40
Q

Chronic osteomyelitis

- Gallium scan

A
  • Increased uptake where leukocytes and bacteria accumulate

* NL scan excludes osteomyelitis

41
Q

Chronic osteomyelitis

- CT scan

A
  • ID sequestra

* Define cortical bone and surrounding soft tissue

42
Q

Chronic osteomyelitis

- MRI

A

• Shows bone margin and soft tissue edema
• Eval reoccurrence after 1 year
• Rim sign: well defined rim of high signal intensity surrounding focus of active dz
Tx

43
Q

Chronic osteomyelitis

- Tx

A
  • Sx is usually needed: remove sequestra, resection of damaged tissue, debridement
  • Abx, duration is controversial
  • Amputation if arterial insufficiency, major nerve paralysis, malignant change, non-functional limb stiffness
44
Q

Chronic osteomyelitis

- Sclerosing Osteomyelitis of Garre’

A
  • Bone thickened and distended but no abscess or sequestra

- Unknown cause, possibly low-grade, anaerobic bacteria

Infectious Disease 2 (13 decks)

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