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3. Equine 3 > SYNOVIAL AND OSSEOUS INFECTIONS > Flashcards

SYNOVIAL AND OSSEOUS INFECTIONS Flashcards

1
Q

Terminology
- Synovial sepsis/infection (synovial membrane)
> what might this refer to?

A
  • Septic/infectious arthritis – joint
  • Septic/infectious tenosynovitis – tendon sheath
  • Septic/infectious bursitis – bursa
  • Joint infection, joint ill
    <><>
    Arthritis: inflammation in the joint
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2
Q

MSK infections in horses affects who? significance? possible origins?

A
  • Musculoskeletal infection is a major affliction in horses of all ages - It can life threatening
  • The origin is varied
    1. Penetrating wound
    2. Soft tissue infection
    3. Hematogenous spread
    4. Iatrogenic by surgical intervention
    5. Iatrogenic by intrasynovial injection
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3
Q

what limb of the horse is susceptible to synovial and bone infection? why?

A

The distal limb of a horse has anatomical disadvantages that increases the risk of synovial and bone infection:
- Poor muscle/soft tissue coverage
- Reduce vascular supply

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4
Q

The normal synovial membrane is capable of what?
when does septic arthritis occur?
Pathogenesis? outcomes?

A
  • Controlling inoculation of microorganism
  • Preventing proliferation and colonization
    <><><><>
    Septic arthritis occurs when the microorganism overcome the defense mechanisms, colonize and establish an infection.
    <><><><>
    After colonization there is a release of enzymes, free radicals and inflammatory mediators – marked synovial inflammatory response
  • In the immediate immune response - predominantly neutrophils
    are rapidly recruited to eliminate the infection
  • There are many inflammatory mediators released – amplifying
    <><><><>
  • The massive inflammatory process
  • The physical effect of the joint effusion
  • The accumulation of fibrin (Nidus for continued infection)
  • The alterations in cartilage biomechanics
    > all of these Contribute to the disease process, and can lead to osteoarthritis
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5
Q

Septic arthritis in foals
- why are they susceptible? origins of this issue in foals? what anatomic areas are susceptible?

A
  • Neonates are more susceptible to infection and septicemia
  • Partial or complete failure of passive transfer can result from:
  • Bacteriemia and septicemia
  • Hematogenous spread into bones and joints
    > Routes of hematogenous spread: lungs, GI, umbilicus
    > bacteria can settle in physis, epiphysis, and synovial membrane
    <><>
  • Septic arthritis can result as well from:
  • Periarticular wound infection
  • Inoculation of the joint by a puncture wound
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6
Q

2.1. Type of infections
A. S-Type (synovial)
- what is it? who gets it? presentation?
- issues with diagnosis?

A
  • Infection only associated with the synovial membrane and fluid
  • Common in young foals <2 weeks old
  • Presentation – multi-limb lameness,
    generalized systemic illness
    <><><><>
  • The diagnosis of a S-type infection might be made in a true E-type where imaging is not sensitive to identify epiphyseal involvement
    > we need time for the bone to degenerate to see those changes on X-rays
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7
Q

2.1. Type of infections
B. E-Type (Epiphysis)
- what is this? who gets it? presentaion?
- common sites?

A
  • Localized to articular epiphyseal bone or bone closed to articular cartilage
  • Common in older foals >2 weeks old
  • Presentation – prior history of
    pneumonia, diarrhea
    <><><><>
    Common sites: distal femur, talus, radius, tibia
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8
Q

2.1. Type of infections
C. P-Type (Physis)
- what is this? who gets it? presentation?
- common sites?

A
  • Localized in long bone physis
  • Common in older foals’ weeks to months
  • Presentation: generally healthy with no
    history of systemic disease
    <><><><>
    Common sites: distal tibia, third metacarpal/metarsal bone, radius
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9
Q

Septic arthritis in adults
Most synovial infections develop from:

A
  • Penetrating traumatic injury
  • Soft tissue infection
  • Iatrogenic following surgery
  • Iatrogenic following intrasynovial injections
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10
Q

Osteomyelitis
- what is this? structures it may invovle?
> osteitis vs osteomyelitis

A

Inflammatory process accompanied by bone destruction caused by an infecting microorganism.
<><>
It can involve
- Bone Marrow
- Cortex
- Periosteum
- Surrounding soft tissue
<><><><>
- Osteitis – if only bone is affected
- Osteomyelitis – if bone and bone marrow is affected

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11
Q

Osteomyelitis
Sources of infection

A
  • Hematogenous
  • Traumatic – secondary to a laceration
  • Iatrogenic – secondary to surgical procedures with/without implants
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12
Q

Osteomyelitis
Pathophysiology

A
  • Adherence and bacteria colonization of the bone, cartilage or implants overcoming the host defense
    <><>
  • Biofilm formation that has four main stages:
  • Reversible attachment
  • Irreversible attachment
  • Growth and differentiation
  • Dissemination
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13
Q

general approach to diagnostics in a case of synovial and osseous infections

A

A. History and physical exam
B. Peripheral blood analysis
C. Diagnostic imaging
D. Synovial fluid analysis
E. Bacterial/fungal culture and susceptibility
F. Pressurizationtest
G. Contrast Study

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14
Q

History and physical exam findigns suggestive of synovial and osseous infection

A
  • Lameness
  • Synovial effusion
  • Edema, cellulitis, swelling
  • Pain on palpation
  • Resistance to passive flexion
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15
Q

Diagnostic imaging modalities used for synovial and osseous infections

A
  1. Radiographs
  2. Ultrasound
  3. Computed tomography
  4. Magnetic resonance
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16
Q

Diagnosis
C. Diagnostic imaging
1. Radiographs
- acute case observations?
- what amount of disease progression required for detection? what amount of time does this correspond to?
- another test which gives us info faster?

A
  • Acute cases fail early osseous lesions
  • 30-50% loss bone density required
  • 21 days after infection - 80-90% of diagnostic accuracy - CT earlier
17
Q

Diagnosis
D. Synovial fluid analysis
- when do we do this?
- important considerations? what do we have to keep in mind when analyzing fluid?

A
  • after imaging
    <><><><>
    1. Remember anatomy
    2. Based on the wound location which joint, tendon sheath,
    bursa can be affected
    3. Which joint compartments communicate
    eg. in stifle joint: some horses have compartments that communicate, while others do not!
  • Femoropatellar joint
  • Medial femorotibial
  • Lateral femorotibial
    4. Collect the samples aseptically
    5. Assess grossly
18
Q

Diagnosis
D. Synovial fluid analysis
- what cells will we find in normal vs infected?
- what else can affect this?

A

normal:
- Total Leukocytes: 50-500
- Neutrophils %: <10
- Mononucelar cells %: >90
- Total proteins: 0.8-2.5
<><><><>
Septic arthritis:
- Total Leukocytes: 20-200 x 10^3
- Neutrophils %: >90 (variable toxic changes)
- Mononucelar cells %: <10
- Total proteins: 4-8+
<><><><>
Local anesthetics:
- Total Leukocytes: 2-10 x 10^3
- Neutrophils %: 60
- Mononucelar cells %: 40
- Total proteins: 2.5-4
<><><><>
Gentamicin:
- Total Leukocytes: 8-40 x 10^3
- Neutrophils %: 50
- Mononucelar cells %: 50
- Total proteins: 4.5-6

19
Q

fungal vs bacterial synovial fluid analysis: considerations

A
  • fungal infections are a nightmare - no good ways known to differentiate at this point
  • most fungal infections have a lower cell count, but still in the abnormal range, and higher proteins compared to bacteria
20
Q

Diagnosis
E. Synovial bacterial (fungal) culture and susceptibility
- how useful?
- when to do it?
- results? how to improve them?

A
  • Gold standard for diagnosis
  • Always submit prior intrasynovial antibiotics
  • Positive culture ranges from 64-89% (proportion of correctly identified cases)
  • The use of blood culture medium improves results 79% > ie. improves odds of detection
21
Q

Diagnosis
F. Pressurization test
- when to do this? what is it?

A
  • In acute injuries (lacerations, puncture wounds)
  • If synovial fluid is not obtained
  • Distend the joint looking for communication with the wound
    > put needle in joint, squirt in water > does it come out the wound?? If yes, it communicates!
22
Q

what test can help us determine communication of a joint with a wound other than a pressurization test?
- when to do this?

A

Contrast study - does contrast come through the wound?
- Do this eg. if you try the pressurization test and its not an obvious result. Maybe it just gets a little wet instead of squirting out, but it is not totally clear to you
> can also give additional info about joint communications

23
Q

Treatment for synovial and osseous infections

A

A. Systemic antimicrobial therapy – broad spectrum until culture results
B. Regional limb perfusions with antibiotics
C. Intraosseous regional limb perfusion with antibiotics
D. Surgical treatment septic synovitis
- Arthroscopic lavage, debridement, fibrin removal
- Lavage with cannulas
- Needle lavage

24
Q

Surgical treatment osteomyelitis

A
  • Debridement curettage
  • Implant removal
  • Bone grafts
  • Antimicrobial-impregnated polymethylmethacrylate implants
    > (keep antibiotics in region for at least 20 mins by reducing bloodlfow or with slow release (as with this implant), various methods such as this one)

3. Equine 3 (9 decks)

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