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Respiratory/Musculoskeletal > M- Infectious Musculoskeletal Diseases > Flashcards

M- Infectious Musculoskeletal Diseases Flashcards

1
Q

What is the typical organisms to cause mono or oligo-articular arthritis?

A

S. aureus

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2
Q

A person presents with systemic infection. They have polyarticular, symmetric involvement. What is the most likely cause? What is treatment?

A

Viral arthritis- they require no therapy and resolve spontaneously without deformity

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3
Q

What are the most likely agents involved in subacute chronic arthritis?

A

Mycobacteria
Fungi
Fastidious bacteria (brucella, borellia burdorferi)

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4
Q

What are the 3 mechanisms of spread into the joints?

What are direct examples of each?

A
  1. Hematogenous (80-90%)
  2. direct inoculation (steroid injection, surgery, trauma, animal bites)
  3. Contiguous spread (diabetic foot ulcer, decubitus ulcer, neonatal osteomyelitis)
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5
Q

What are underlying joint abnormalities that predispose to septic arthritis?

A
  • RA, gout , pseudogout, OA
  • Charcot joint (neuropathic joint) associated with syphilis/diabetes
  • prior surgery, steroids, prosthesis
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6
Q

What systemic factors increase the risk of septic arthritis?

A
  • Diabetes
  • Immunosuppression
  • IVDA
  • Concomitant infections (UTI, endocarditis, pneumonia, skin
    infections)
  • Elderly age
  • STD risk factors for GC
  • chronic renal or liver disease
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7
Q

What joint is most involved in septic arthritis in adults and kids?

A

Knee>hip> ankle

*weight bearing joints

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8
Q

An IV drug user with RA and a skin rash comes in. What organism could cause his septic arthritis?

A

S. aureus

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9
Q

What bacteria are associated with diabetes and immunocompromised people?

A

Strep pyo, pneumo, agalactinae

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10
Q

If the person has a high risk of STDs, what would you be suspicious was the cause of their septic arthritis?

A

neisseria gonorrhea

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11
Q

What bacteria would you suspect to be the cause of septic arthritis if the person is an IVDA with a UTI and are immunocompromised?

A

G- rods

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12
Q

A patient has vascular disease and is a diabetic with an abscess. What is the likely cause of the septic arthritis?

A

Anaerobes/ mixed bacteria from skin flora

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13
Q

Is septic arthritis usually monoarticular, oligoarticular or polyarticular?
What type of joint is the most commonly involved?

A

Mono or oligo
It usually is a diarthrodial joint
Knee, weight bearing joints of lower extremities

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14
Q

What is the common physical exam presentation of septic arthritis?

A
  1. monoarticular/oligoarticular
  2. red, swollen painful joint
  3. decreased range of motion, pain more intense with extension
  4. fever/malaise
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15
Q

What are the lab values seen with septic arthritis?

A

elevated ESR and CRP

WBC with left shift

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16
Q

What is needed to make definitive diagnosis of septic arthritis?

A

Arthrocentesis with:
WBC >50,000 (neutrophils)
Gram stain , culture

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17
Q

You are examining a patient with a painful swollen joint that gets more painful with flexion. You do arthrocentesis and note crystals and WBC above 50,000. You also get a positive culture. What is the likely scenario?

A

bacterial superinfection of a pseudogout or gout joint

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18
Q

What is seen on radiograph for septic arthritis?

A

Early:
soft tissue swelling around the joint
fad pad edema

Later:

  • periarticular osteoporosis
  • joint space narrowing
  • periosteal reaction
  • marginal/central erosions
  • destruction of subchondral bone
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19
Q

What are the 2 major steps for treatment/management of infective arthritis? Explain how both are done.
How long is treatment given?

A
  1. Drainage
    - serial, daily needle aspirations
    - arthroscopic surgical drainage
    - open surgical drainage (hip or shoulder)
    - removal of prosthetic with debridement of tissue
  2. antibiotic regimen
    - empiric therapy directed at the most common pathogen: G+ cocci
    - definitive therapy based on gram stain and culture

2 to 4 weeks esp for staph and G- rods
2 weeks for gonococcal

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20
Q

What is the main mechanism of infection of prosthetic joints?
How does this differ from native joints?

A

Direct inoculation (usually intraoperatively)

This differs from native joints because most native joints are infected hematogenously.

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21
Q

What are the 4 major local factors that increase the risk of infecting a prosthetic joint?

A
  1. joint has a microscopically rough surface and bacteria can hide
  2. polymethylmethacrylate cement inhibits PMNs
  3. biofilms inhibit phagocytosis and antibiotic penetration
  4. postoperative wound ischemia, hematoma, suture site or skin infections
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22
Q

What is the predominant organism that causes disease in a prosthetic joint?

A

coagulase-negative staphylococci is equal or exceeds s. aureus

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23
Q

How is the presentation of prosthetic joint infection different from native joint?

A

It is less severe, more chronic

  1. subacutely ill for months
  2. progressive joint pain
  3. fever, swelling, draining of pus from the joint
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24
Q

How do you diagnose prosthetic joint infection?

A

Arthrocentesis with:
WBC >50,000
Positive gram stain and culture

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25
Q

What are the characteristic findings on radiograph of an infected prosthetic?

A
  1. lucency around the interface of bone and prosthesis
  2. loss of correct anatomical alignment
  3. movement of prosthetic device
  4. reaction of periosteum of adjacent bone
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26
Q

What is the necessary protocol for therapy after you have diagnosed infection of a prosthesis?
What are the 2 techniques?

A
  1. Removal, debridement, replacement of prosthetic joint

1-step :

  • more frequent in Europe
  • relatively avirulent organisms
  • Take out prosthetic, debride and irrigate at operative site, implant second joint anchoring it with polymethylmethacrylate cement impregnated with gentamycin and vanco.

2-Step:

  • US
  • first operation, remove infected prosthetic and debride. Insert a spacer impregnated with antibiotics
  • 6 weeks of IV antibiotics
  • second operation a new prosthetic is inserted
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27
Q

What is therapy for prosthetic infection if the prosthetic CANNOT be removed?

A

chronic suppressive antibiotics that lasts YEARS.

The organism must be avirulent and sensitive to oral antibiotics.

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28
Q

What are the 2 syndromes caused by neisseria gonorrhea?

Who is likely to get infected by this?

A

Sexually active people under 30, usually women where 1/3 to 1/2 occur during menses, pregancy, or postpartum.

  1. hematogenous arthritis
  2. tenosynovitis and dermatitis (papular, macular, pustular lesions on necrotic base)
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29
Q

What are the biggest risk factors (biochemically) for Disseminated gonococcal infection (DGI)?

A

deficiency in terminal complement components from C5 to C9

30
Q

What are the unique characteristics of DGI strains of bacteria?

A
  1. resistant to killing by human serum (defective C5-C9 so no complement is activated)
  2. nutritional deficiencies - must be grown on chocolate agar
31
Q

What joints are most frequently affected by DGI? Is it mono, oligo or polyarticular?

A

It is mono or oligoarticular and usually involves

Knees>wrists> ankles

32
Q

When you are suspicious of DGI, what 2 things must you do to look for cultures?

A
  1. aspiration of the joint yields culture 25-50% of the time
  2. culture the oropharynx, genitalia, and rectum to increase culture yield
33
Q

What test has been replacing/augmenting culture of neisseria gonorrhea?

A

Nucleic Acid Amplification Tests with PCR

34
Q

What is treatment for N. gonorrheal arthritis?

A

Ceftriaxone for 2 weeks

35
Q

When does viral arthritis usually occur? When does it resolve?
What is the most common virus in humans?

What are other common causes of viral arthritis?

A

It occurs in the setting of systemic infection and resolves when the illness is done.

Parvovirus B19

Other cause:
Hep A and B, HIV, HTLV-1

36
Q

A child comes in with a fever, coryza, headache and malaise. You note a red rash on his cheek and a reticular rash on his legs and trunk.
What is the likely cause?

A

Parvovirus B19 bc of the slapped cheek rash.

37
Q

What does a parvovirus B19 viral infection show on blood tests?

A

It arrests at the pronormablast stage of RBC development so the person with the infection can present with anemia

38
Q

A man comes in with nonfocal febrile syndrome and polyarthralgia.
He has an inflamed MCP on his hand making you suspicious of RA. 2 weeks pass and there is complete resolution.

What is the likely cause?
How is diagnosis made?

A

viral arthritis

Diagnose with:

  1. serum IgM to parvovirus
  2. PCR on joint fluid, synovium, bone marrow
39
Q

Describe the onset and symptoms of chronic infectious arthritis.
What organisms are usually involved?

A

Symptoms are:

  1. monoarticular involvement
  2. slow onset, indolent course
  3. lack of systemic symptoms like fever
  4. pain without inflammation

Syphilis, lyme disease, whipples disease, TB, fungal

40
Q

What fungal pathogens can cause chronic infectious arthritis?

How can you diagnoses which is present?

A

Cocci
Blasto
Paracocci

The synovial fluid is purulent and organisms can be seen microscopically.
Culture is + but takes day-wks to grow,

41
Q

What is medical therapy for a fungal cause of chronic infectious arthritis?

A

You do NOT need to operatively drain.

Give antifungal drugs for months or years

42
Q

Describe the arthritis caused by MTb.

onset, # of joints involved, population affected, what joints are most affected

A

Affects children and young adults and is a slow progressive monoarticular arthritis.
It usually affects the legs.

Risk factors:
immunocompromised
prior arthritis
povery, incarceration, alcohol, drugs

43
Q

How is MTb chronic infectious arthritis diagnosed?

A
  1. Skin test is + in 90%
  2. sample synovial fluid :
    - WBC >10-20,000
    - culture is +
    - acid fast bacilli (+ 10-20% of the time)
  3. synovial biopsy
    - granulomata with caseating foci (90%)
44
Q

What are the two most common locations for a septic bursa?

A

Olecranon and prepatellar bursa

45
Q

What is the pathogenesis by which a septic bursa forms?

A
  1. trauma to the skin over the bursa
  2. cellulitis
  3. bursa gets infected by spread from a contiguous focus (skin)

Occasionally spread can be from direct implantation (thorn, needle)

46
Q

What organism causes the majority of septic bursitis?

A

S. aureus (80%)

strep (20%)

47
Q

What is noted on physical exam for septic bursa?

A

Affected bursa is red, swollen painful and tender.

Pain increases with flexion (as opposed to septic arthritis which gets painful with extension)

48
Q

How is diagnosis of septic bursa made?

A

needle aspiration for cell count, crystal analysis, gram stain, and culture

49
Q

What are the 3 differential diagnoses for septic bursitis?

A
  1. Trauma- swollen but not painful tender or erythematous. ROM is normal
  2. crystal disease- swollen red painful and tender
  3. Infection -swollen red painful and tender with decreased range of motion and increased pain with extension of the joint
50
Q

A patient presents with a swollen bursa. It is not tender, painful or erythematous.
Aspiration yields a yellow serous fluid, and slight traces of blood.
Cultures are negative. What is the likely cause?

A

Trauma

51
Q

A patient presents with swollen, red, painful, bursa.
Aspiration yields elevated WBC with lots of neutrophils.
Crystal analysis is positive and cultures are negative. What is the likely cause of the bursitis?

A

Crystal disease

  • gout
  • pseudogout
52
Q

A patient presents with swollen red painful bursa. There is decreased ROM and increased pain with extension. Aspiration shows elevated WBC and PMNs. Culture is positive and crystals are negative. What is the likely cause of the swelling?

A

Infection

53
Q

What is treatment for septic bursitis?

A
  1. empiric antibiotics
  2. altered antibiotics based on sensitivities
  3. removal of bursa if medicine fails
54
Q

What are the 3 most common bones involved with osteomyelitis?

A
  1. long bones of extremities (Legs»arms)
  2. bones of the feet (diabetics/PVD)
  3. vertebral column
55
Q

What is the most common single organism that causes osteomyelitis?
What is the usual scenario where the infection will be polymicrobial?

A

Usually S. aureus.

It can be polymicrobial usually in osteomyelitis of the foot in diabetics

56
Q

What is the main differential diagnosis for osteomyelitis?

A

Malignancy

57
Q

What do lab tests show for osteomyelitis?

How long does it take to see bony abnormalities on the radiograph for osteomyelitis?

A

Elevated CRP and ESR.
In acute osteomyelitis- elevated WBC
In chronic osteomyelitis- normal WBC

You don’t see any bony changes in the first 2 weeks of infection so get a bone scan, CT, MRI

58
Q

What is the duration of therapy for osteomyelitis?

A

6 weeks minimum for adults

59
Q

What is the most common cause of osteomyelitis in prepubertal children?
What is the mechanism by which the bone gets infected? How does this mechanism differ if the child is less than 1?

Which bones are most commonly affected?

A

Acute hematogenous osteomyelitis

In children, bacteria spreads to the metaphysis of bone where bacteria seed in closed capillary loops.

If the child is

60
Q

What is treatment for acute hematogenous osteomyelitis in children?

A

Antibiotics for 3 weeks

61
Q

What adults are most likely to get acute hematogenous osteomyelitis?

A
  1. IVDA
  2. dialysis patients
  3. indwelling central catheters
62
Q

How do most cases of verterbral osteomyelitis originate?

Once in the vertebrae, where can the infection extend?

A
  1. Hematogenous seeding of the vertebral bodies
  2. direct implantation from ortho hardware

It can spread to surrounding soft tissue:

  • paraspinous muscle abscesses
  • psoas abscess
  • spinal epidural abscess
63
Q

A patient presents with slowly progressive back pain. They are having night sweats/fever. They were relatively afebrile until very late in the course of the back pain. You palpate along the vertebral column and note tenderness. What 5 organisms are on the differential?

A

This is vertebral osteomyelitis

  1. S. aureus
  2. Coagulase negative staph (if prosthetics)
  3. Brucella (if exposed to animal reservoirs)
  4. MTb
  5. Fungal
64
Q

What is the imaging modality of choice for vertebral osteomyelitis?

A

MRI because it also gives a good view of the surrounding tissue

65
Q

What is the gold standard for diagnosis of verterbral osteomyelitis?

A

Bone biopsy obtained:

  1. open surgical
  2. CT-guided
66
Q

What is the minimum duration of antibiotic therapy for vertebral osteomyelitis?
What would indicate a need for surgery?

A

4-6 weeks

Surgery is necessary if the spine is mechanically unstable or there are large paravertebral or epidural abscesses.

67
Q

What is the pathogenesis for how osteomyelitis develops in a diabetics foot?

A
  1. peripheral neuropathy so they don’t feel minor or major injury
  2. Chronic ulcers develop as a result
  3. Ulcers provide portal of entry for bacteria which spreads to bone by contiguous spread
68
Q

What are the major risk factors for the development of foot ulcers in diabetics?

A
  1. poor glycemic control
  2. diabetes >10 years
  3. cardiac disease
  4. diabetic retinopathy
  5. diabetic neuropathy
69
Q

What are the diagnostic tests for osteomyelitis in diabetics? What is treatment?

A

Diagnostic:

  1. ESR, CRP and WBC elevation
  2. probing open ulcer and hitting bone
  3. SWAB IS NOT HELPFUL

Treatment: combo surgery and medicine

  • broad spectrum antibiotics bc polymicrobial infection
  • recurrence is frequent after antibiotic therapy
  • requires amputation
70
Q

What is the usual organism that causes diabetic osteomyelitis?

A

Polymicrobial: mix of S. aureus, G- rods, Pseudomonas, anaerobics

Respiratory/Musculoskeletal (36 decks)

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