SYNOVIAL AND OSSEOUS INFECTIONS Flashcards
(24 cards)
Terminology
- Synovial sepsis/infection (synovial membrane)
> what might this refer to?
- Septic/infectious arthritis – joint
- Septic/infectious tenosynovitis – tendon sheath
- Septic/infectious bursitis – bursa
- Joint infection, joint ill
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Arthritis: inflammation in the joint
MSK infections in horses affects who? significance? possible origins?
- 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
what limb of the horse is susceptible to synovial and bone infection? why?
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
The normal synovial membrane is capable of what?
when does septic arthritis occur?
Pathogenesis? outcomes?
- Controlling inoculation of microorganism
- Preventing proliferation and colonization
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Septic arthritis occurs when the microorganism overcome the defense mechanisms, colonize and establish an infection.
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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
Septic arthritis in foals
- why are they susceptible? origins of this issue in foals? what anatomic areas are susceptible?
- 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
2.1. Type of infections
A. S-Type (synovial)
- what is it? who gets it? presentation?
- issues with diagnosis?
- 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
2.1. Type of infections
B. E-Type (Epiphysis)
- what is this? who gets it? presentaion?
- common sites?
- Localized to articular epiphyseal bone or bone closed to articular cartilage
- Common in older foals >2 weeks old
- Presentation – prior history of
pneumonia, diarrhea
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Common sites: distal femur, talus, radius, tibia
2.1. Type of infections
C. P-Type (Physis)
- what is this? who gets it? presentation?
- common sites?
- Localized in long bone physis
- Common in older foals’ weeks to months
- Presentation: generally healthy with no
history of systemic disease
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Common sites: distal tibia, third metacarpal/metarsal bone, radius
Septic arthritis in adults
Most synovial infections develop from:
- Penetrating traumatic injury
- Soft tissue infection
- Iatrogenic following surgery
- Iatrogenic following intrasynovial injections
Osteomyelitis
- what is this? structures it may invovle?
> osteitis vs osteomyelitis
Inflammatory process accompanied by bone destruction caused by an infecting microorganism.
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It can involve
- Bone Marrow
- Cortex
- Periosteum
- Surrounding soft tissue
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- Osteitis – if only bone is affected
- Osteomyelitis – if bone and bone marrow is affected
Osteomyelitis
Sources of infection
- Hematogenous
- Traumatic – secondary to a laceration
- Iatrogenic – secondary to surgical procedures with/without implants
Osteomyelitis
Pathophysiology
- 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
general approach to diagnostics in a case of synovial and osseous infections
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
History and physical exam findigns suggestive of synovial and osseous infection
- Lameness
- Synovial effusion
- Edema, cellulitis, swelling
- Pain on palpation
- Resistance to passive flexion
Diagnostic imaging modalities used for synovial and osseous infections
- Radiographs
- Ultrasound
- Computed tomography
- Magnetic resonance
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?
- Acute cases fail early osseous lesions
- 30-50% loss bone density required
- 21 days after infection - 80-90% of diagnostic accuracy - CT earlier
Diagnosis
D. Synovial fluid analysis
- when do we do this?
- important considerations? what do we have to keep in mind when analyzing fluid?
- after imaging
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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
Diagnosis
D. Synovial fluid analysis
- what cells will we find in normal vs infected?
- what else can affect this?
normal:
- Total Leukocytes: 50-500
- Neutrophils %: <10
- Mononucelar cells %: >90
- Total proteins: 0.8-2.5
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Septic arthritis:
- Total Leukocytes: 20-200 x 10^3
- Neutrophils %: >90 (variable toxic changes)
- Mononucelar cells %: <10
- Total proteins: 4-8+
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Local anesthetics:
- Total Leukocytes: 2-10 x 10^3
- Neutrophils %: 60
- Mononucelar cells %: 40
- Total proteins: 2.5-4
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Gentamicin:
- Total Leukocytes: 8-40 x 10^3
- Neutrophils %: 50
- Mononucelar cells %: 50
- Total proteins: 4.5-6
fungal vs bacterial synovial fluid analysis: considerations
- 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
Diagnosis
E. Synovial bacterial (fungal) culture and susceptibility
- how useful?
- when to do it?
- results? how to improve them?
- 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
Diagnosis
F. Pressurization test
- when to do this? what is it?
- 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!
what test can help us determine communication of a joint with a wound other than a pressurization test?
- when to do this?
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
Treatment for synovial and osseous infections
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
Surgical treatment osteomyelitis
- 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)
