Lecture 3: Septic synovial structures

What is the etiology of septic arthritis and tenosynovitis in adults?

• Invade the joint or tendon sheath

• Joint injection (22%)

• Joint surgery

• Local extension of periarticular infection

• Tissue necrosis from wound

What is the etiology of septic arthritis and tenosynovitis in foals?

• Hematogenous spread from septic foci (GI, respiratory, umbilical tract)

• Infection in epiphyseal bones hat breaks into the joint space

Most common isolates in wounds?

Mixed gram-positive and gram-negative species

Common pathogens that cause iatrogenic septic arthritis?

Staph aureus and fungal species

When are foals at the highest risk for septic arthritis?

first 30 days of life

How many joints are affected in newborn foal?

multiple

How many joints are typically infected in juvenile foals?

Single joint

What gram positive bacteria are commonly found?

• Alpha or beta streptococcus

• Actinobacillus

• Staph aureus, epidermidis

• R. equi

What gram negative bacteria can cause septic arthritis?

• E. coli

• Salmonella

• Enterobacter

• Proteus

• Klebsiella

What is the pathophysiology septic synovial infections?

• Bacteria in oculus overcome synovial defenses

• Immediate inflammatory response (II-6 and II-B)

  • Neutrophils recruited → phagocytize bacteria and release collagenase, lysozymes, and metalloproteinases

• Accumulation of fluid w/in the joint effusion

• Inflammation of the synovium

• Fibrin deposition w/in joint

• Degradation of cartilage and subchondrol bone

How do you diagnose septic joint disease?

• History (recent trauma, recent joint injection, lameness, analgesic administration)

• PE (Febrile, diarrhea, umbilical infection in foals)

• Peripheral blood analysis

• Synovial fluid analysis

• Joint wash

• Cytology

• Culture

• Radiographs

• US

Blood analysis results in adults with septic synovial structures?

Normal to slightly elevated wbc, increased fibrinogen, increased SAA

Expected blood analysis results for foals with septic synovial structures?

Systemic elevations in WBC, fibrinogen, and SAA

How do you perform a synovial fluid analysis?

• Use aseptic techinique to collect

• Arthtrocentesis of joint in areas distant from wounds

• Red top for bacterial ID and purple tube for analysis

Synovial fluid values:

NCC >300,000 cell/uL (Normal: <500 cells/uL), 90% neutrophils

TP >4.0 gm/dl (Normal: <2.5 gm/dl)

Diagnosis?

Sepsis

When is a joint wash used?

If synovial fluid cannot be obtained

Turbidity, hemorrhagic, flocculent material

Infection

Cytology results:

• >80% degenerate neutrophils

• NCC >30,000 ncc/ul

• Viscosity reduced

• pH 6.2-6.9

• Lactate= 7-12 moles/L

• Glucose >2.2 mmol/L

Diagnosis?

Septic joint

What kind of cultures can you use to culture infection in foals?

Blood culture bottles

What should you evaluate radiographs for?

Osteitis, osteomyelitis, physitis, OA, fracture

What joints are more easily evaluated with US?

Shoulder and hip

How do you perform arthroscopy?

• 5-20 L sterile polyionic fluids

• Standing, sedated

• Repeat daily until NCC < 30,000 cells/uL

What are the benefits of arthotomy?

• Severely infected joints

• Constant drainage to promote comfort

Why don’t you use DMSO to lavage?

• Suppresses cartilage metabolism

• Decreased proteoglycan synthesis

• Chrondrocyte death

Why don’t we use Chlorhexadine or betadine to lavage?

Irritating to joing

What is the ideal antimicrobial for treating septic arthritis?

• Good suspectibility of common infective agents

• Bactericidal, not static

• Ability to reach therapeutic levels in synovial fluid and bone

• Minimal toxicity

• Minimal side effects

• $

When should you start antimicrobial therapy?

Immediately

Antibacterials of choice for gram positive?

Penicillin, ampicillin, Cephalosporin (cetiofur, cefazolin, cefotaxime)

What are the antibiotics of choice for gram negative?

Aminoglycoside (Gentocin, amikacin), fluoroquinolones (enrofloxacin)

How long should you treat initially?

If no improvement change antibiotics in 72 hours. Treat until synovial fluid parameters return to normal with IV

Benefits of intra-articular antibiotics

• Avoidance of systemic toxic

• Can use cost-prohibitive drugs in small volume

How far behind do radiographic changes lag behind CS?

14 days

What antibiotics can be used in intra-articular treatments?

Amikacin, Gentocin, Cefazolin, Ceftiofure, Meropenem, Imipenem

What antibiotics can be used in regional limb perfusions?

Ceftiofur, Ceftriaxone, Meropenem, Imipenem, Dexmethasone

What is the indication for antibiotic-impregnated PMMA beads?

Osteomyelitis

What other supportive care should be provided?

• NSAIDs (careful in foals)

• Gastroprotectants (Omeprazole)

• Surpass (Applied topically)

• Joint support

What septic synovial structures care the worse prognosis?

Navicular bursae and coffin joints

What is a common consequence of septic arthritis and tenosynovitis? a) Mild discomfort b) Life-threatening condition c) Temporary lameness d) Improved joint function

b) Life-threatening condition

Which of the following is NOT a route of delivery of antimicrobials to the joint? a) Intra-articular b) Regional limb perfusionc) Continuous infusion via catheter d) Oral administration as the sole method

d) Oral administration as the sole method

Which of the following is considered a surgical emergency? a) Mild sprain b) Septic arthritis c) Chronic lameness d) Minor wound

b) Septic arthritis

What is a primary cause of septic arthritis? a) Old age b) Wound that invades a jointc) Dietary imbalance d) Lack of exercise

b) Wound that invades a joint

What percentage of septic joints are caused by joint injections? a) 10% b) 22% c) 35%d) 50%

b) 22%

In foals, what is the most common way for septic arthritis to develop? a) Wound contamination b) Hematogenous spread from septic foci c) Joint injection d) Local extension of a periarticular infection

b) Hematogenous spread from septic foci

What are common sources of hematogenous spread in foals? a) Gastrointestinal, respiratory, and umbilical tract b) Skin wounds c) Joint injections d) Dental infections

a) Gastrointestinal, respiratory, and umbilical tract

What type of bacteria are most commonly found in adult septic arthritis cases from wounds? a) Mixed gram-positive and gram-negative species b) Only gram-positive c) Only gram-negative d) Fungal species

a) Mixed gram-positive and gram-negative species

What bacteria is often seen in iatrogenic septic arthritis in adult horses? a) E. coli b) Salmonella c) Staphylococcus aureusd) Rhodococcus equi

c) Staphylococcus aureus

What is a risk factor for septic arthritis related to joint treatment? a) Use of vitamins in joints b) Use of corticosteroids in the joint c) Use of hyaluronic acid in joints d) Use of antibiotics in joints

b) Use of corticosteroids in the joint

What is the most common joint affected in juvenile foals with septic arthritis? a) Multiple joints b) A single joint c) Hock d) Carpus

b) A single joint

What is the initial inflammatory response in septic arthritis due to? a) Il-6 and Il-B b) Collagenases and lysozymes c) Metalloproteinases d) Fibrin

a) Il-6 and Il-B

What is the typical white blood cell count in adults with septic arthritis? a) Significantly elevated b) Normal to slightly elevated c) Significantly decreased d) Variable, depending on the bacteria

b) Normal to slightly elevated

What is considered a septic white blood cell count in synovial fluid? a) < 500 cells/ulb) > 10,000 cells/ul c) > 30,000 cells/ul d) > 50,000 cells/ul

c) > 30,000 cells/ul

What is the primary cell type found in septic synovial fluid? a) Lymphocytes b) Monocytes c) Neutrophils d) Eosinophils

c) Neutrophils

What can be done if synovial fluid can not be obtained? a) Wait until there is fluid b) Use DMSO solution to produce fluidc) Inject sterile saline and withdraw for analysisd) Nothing, culture cannot be done

c) Inject sterile saline and withdraw for analysisd) Nothing, culture cannot be done

What is the significance of the absence of bacteria on cytology of synovial fluid? a) Does not negate sepsis b) Indicates no infection c) Indicates a viral infection d) Indicates a fungal infection

a) Does not negate sepsis

What is a common treatment for septic arthritis? a) Rest and anti-inflammatories onlyb) High volume lavage with sterile fluids c) DMSO solutions d) Aseptic solutions

b) High volume lavage with sterile fluids

Why should DMSO solutions NOT be used for joint lavage? a) Suppresses cartilage metabolism b) Increases inflammationc) Causes no harm d) Improves proteoglycan synthesis

a) Suppresses cartilage metabolism

When should antimicrobial therapy be initiated in septic arthritis cases? a) After culture results are returned b) Once the animal is stable c) Immediately d) Only with an open wound

c) Immediately

Which of the following is NOT a route of delivery of antimicrobials to the joint? a) Intra-articular b) Regional limb perfusionc) Continuous infusion via catheter d) Oral administration as the sole method

d) Oral administration as the sole method