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Musculoskeletal System > 3 - Ortho: Infections > Flashcards

3 - Ortho: Infections Flashcards

1
Q

What are the characteristics of bone infections that are fundamental differences from other infections?

A

Blood supply is not as rich as other systmes
Mechanical function is disturbed by infection in bone and worsens with longevity (Treat ASAP)
Surgical implants increase risk of infection

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2
Q

What is the most common organism responsible for orthopedic infections?

A

S. Aureus
Initially binds to host extracellular matrix proteins
Release of toxins damages host cells and elicits

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3
Q

Describe the virulence of S. Aureus

A

50% have a plasmid mediated resistance to antimicrobials
Excretion of Protein A that inactivates IgG
Production of a capsular polysaccharide that inhibits phagocytosis
Produces a biofilm to seclude the organism

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4
Q

Describe the diagnostic modalities for Ortho infections?

A 
CBC with differential
ESR (inc. for 1st days)
CRP (inc. within 6 hrs)
Blood Culture
Tissue Culture
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5
Q

Prior to treating a suspected ortho infection, what must the physician do?

A

Get a blood culture for a definitive dx prior to treatment

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6
Q

What is the earliest finding seen in imaging of patients with ortho infections?

A

soft-tissue swelling evident on radiograph

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7
Q

What types of bone scanning are indicated for the dx of osteomyelitis?

A

Standard is the Three Phase bone scan (Technetium [Tc99]), and sometimes Indium 111 leukocyte labeled

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8
Q

What does bone scanning detect that allows for dx of an infection?

A

Bone scans reflect inflammatory changes and reaction in the bone.

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9
Q

Describe the uptake and excretion of Tc99

A

Uptake related to osteoblastic activity/regional blood flow (increased = show up on scan = inflammation)

Excreted by the kidneys (notable in pt with renal issues)

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10
Q

Describe the 3 phases of a Tc99 bone scan

A

Flow phase: demonstrates blood flow

Eq. phase: distribution of istope in extracellular space

Delayed phase: osteoblastic activity (positive in osteomyelitis, tumors, DJD, post-surgical, trauma

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11
Q

Describe the changes in activity in the certain phases of triple phase scanning for osteomyelitis, cellulitis, and DJD.

A

Cellulitis: increased flow and eq./ decreased delay

Oseomyelitis: increased all phases

DJD: increased in delayed/not in flow or eq

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12
Q

Describe how indium bone scans differ from Tc99.

A

Indium are costly and complex
Blood removed at 2, 4, and 24 hours and indium is mixed with the blood sample
It is the most sensitive modality

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13
Q

What is an MRI used for in dx of a bone infection?

A

To assess the extent of marrow involvement

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14
Q

What is the conclusive course of modality recommended in dx of bone infections?

A

Radiographs followed by Triple Phase bone scan and MRI if available.

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15
Q

Describe osteomyelitis in general.

A

Inflammation of bone caused by infecting organism

Can involve marrow, cortex, periosteum, and surrounding tissue.

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16
Q

Describe the 3 classes of osteomyelitis.

A

Based on pathogenesis: Hematogenous, Traumatic, Contiguous

Based on duration; Acute, subacute, chronic

Based on age: Adult or Ped

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17
Q

Describe Acute Hematogenous osteomyelitis

A

Most common in children (due to slowed blood flow in metaphyseal arteries)
Caused by bacteremia (bacteria in the blood)
Involves metaphysis of growing long bones
Can erode cortex, causing subperiosteal abscess and eventual sequestra and chronic osteomyelitis

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18
Q

Where does hematogenous osteo most commonly occur in the body?

A

Hip

19
Q

Describe the most common causative pathogens for osteomyelitis

A

Staph aureus in older children and adults

Pseudomonas - in IV drug usuers and puncture wounds

Fungal infections common in patients on long term pickline

Salmonella in patients with hemoglobinopathy (e.g. sickle cell)

20
Q

Describe subacute osteomyelitis

A

insidious onset, fever and systemic symptoms
WBC normal, ESR elevated
Brodie Abscess - localized osteomyelitis with metaphyseal and epiphyseal involvement

Lytic lesion with rim of sclerotic bone
Often confused with a neoplasm

21
Q

A small round dark spot surrounded by bright white bone on xray is known as?

A

Brodies abscess - localized osteomyelitis

22
Q

Describe the erradication of osteomyelitis once its reached its chronic fomr

A

Usually cant be erradicated unless surgical intervention is done.

23
Q

Define the terms involucrum and sequestrum.

A

Sequestrum; dead bone or purulent matter where bone should be
Involucrum: dead bone around a sequestrum

24
Q

What bug has a high correlation with osteomyelitis resulting from a puncture wound?

A

Pseudomonas

25
Q

What is the significance of sequestrum with regard to treatment of bone infections.

A

The sequestrum is separated from the living bone and haversian canals are blocked making antibiotics unable to penetrate.

26
Q

How are sequestra formed

A

Infections leads to an increased in intramedullary pressure from inflammatory exudates

Periosteum becomes stripped from osteum, and leads to vascular thrombii

Necrosis due to lack of blood supply

27
Q

Describe an involucrum and its significance.

A

it is bone formed around a sequestrum, can form a sinus or sinuses that may allow dead bone and pus to pass out of the sequestrum

28
Q

What is the term for sequestrum removal surgery?

A

saucerization

29
Q

What is the most common cause of septic arthritis in adults?

A

Neisseria gonorrhoeae

Mycobacterium or fungal infections in immunocomprimised.

30
Q

What value is commonly indicative of an infection in the bone?

A

40-60% PMNs

31
Q

Describe transient synovitis of the hip

A

Age 3-8 years
Presents with acutely irritable hip, presentation my be indistinguishable from septic arthritis
WBC>12,000, ESR >40mm/h are diagnositc

32
Q

Describe the course of tuberculosis and why it can be associated with orthopedic infections.

A

TB affects every organ system

50% with osseous involvement

33
Q

Where in the skeleton does a TB infection most commonly show bone effects?

A

The lumbar and lower thoracic spine (Pott’s Disease)

MRI of the spine to help confirm dx

34
Q

Describe the effects of syphillis on the MSK system

A

T. Pallidum
Causes chronic arthralgias, development of charcot neuroarthropathy

Treatment - penicillin benzanthine

35
Q

Describe the 3 possible types of necrotizing fasciitis.

A

Flesh eating disease caused by bacterial infections in the deeper layers of skin and subcutaneous tissue, eats through fascial layers
Type I - polymicrobial
Type II - monomicrobial (S. Pyogenes)
Type III - gas gangrene (clostridia)

REVIEW SLIDE ON LAYERS OF SKIN W/ INFECTION TYPES @ EACH LEVEL

36
Q

Name some causative agents of necrotizing fasciits.

A

Strep A, Strep Pyogenes, Recently MRSA

Release exotoxins which activates T-cells and cytokines

Aggressive debridement and removal of infected tissue necessary (amputations are very common)

37
Q

What is diskitis?

A

Hematogenous infection of disk and vertebral body

Presents with severe pain and limited motion, narrowing of disc space

38
Q

What is the most common cause of diskitis?

A

staph aureus

39
Q

What is the most important symptom of an infected joint replacement following surgery.

A

Pain may be the only symptom

May also show increased range of motion, drainage, history of recent dental procedure

40
Q

What type of diagnostic testing can be done for diagnosis of an infected joint replacement?

A 
Bone Scan (triple phase or indium)
Arthrogram (aspirate joint)
Xray
41
Q

Discuss the course of treatment for an infected total joint replacement?

A

Systemic antibiotics for 4-6 weeks
Debridement of joint and retention of prosthesis
One stage revision - exchange arthroplasty
Two stage revision - insert antibiotic spacer then re-do arthroplasty
Suppressive antibiotics

42
Q

Describe the 3 stages of lyme disease

A

1 - early localized skin lesion (erythema migrans)
2 - early disseminated disease (neurological and cardiac) meningoencephalitis
3 - late stage (MSK symptoms) - monoarthritis usually in knee, arthralgia

May be an autoimmune response

43
Q

Describe the management of human bites..

A

C&S, Debride, C&S, Leave wound open (unless on face or neck), Tetanus Booster,

Rx - Augmentin 875mg PO, Doxycyclin if allergic to penicillin

IV Rocephin if admitted to hospital

44
Q

Describe the symptoms and treatment of a brown recluse spider bite…

A

Causes necrotising arachnoidism
Inflammation, eschar, tissue necrosis, sloughing
Syringomyelin D2 responsible for erythrocyte lysis

Musculoskeletal System (21 decks)

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