LA MS 14: Septic OA Flashcards
Septic OA
EMERGENCY
Painful - support limb laminitis
IFX –> IFM
–bacteria: hyaluronidase, cytolytic toxins
–Synovial cells: IL-1B, prostaglandins
Eliminating IFX early = key
Irreversible cartilage degeneration - tx goal is to minimize OA
Classification of Septic Arthritis - hematogenous
SEPTic S type = synovium E type = epiphysis P type = physis T type = tarsal bone
Classification of Septic Arthritis - Non hematogenous
Puncture wound
Contiguous soft tissue
Septic Arthritis in Foals - Neonatal blood supply
In the growth plate, have transphyseal vessels that communicate btw primary and epiphysis artery. Predisposes IFX at growth plate (physis) in foals
- -over time, lose these connections
- -Bacteria more likely to lodge in small capillaries
- -as being vessels, being degraded, bacteria more likely to get stuck so more challenging to dx and treat
Type S
Synovial
Septic arthritis resulting from inoculation of the synovial membrane
Often see gas-producing bacteria or open communication to outside world
Type E
Subchondral bone IFX present
epiphysis
Type P
Physis
Physeal IFX on the metaphyseal side of the growth plate
Often appears lytic
–remember RAD changes always lag behind
Type T
Tarsal bones (or carpal bones)
IFX of small tarsal or carpal bones esp in premature foals
Sequela
–collapse and angular limb deformity
Foal vs Adult
Prog usually worse in foals
- -hematogenous
- -complications from the septicemia
- -multiple jts = decreased racing prognosis
- -also osteitis, osteomyelitis, physitis
Other complications assoc w/ foals
May have
–septic arthritis only
–septic physitis only
–septic arthritis and physitis
–septic osteomyelitis, physitis
–septic arthritis, physitis and osteomyelitis
BEWARE - premature closing and angular limb deformities
Dx - hx (foals)
FOALS ARE OFTEN FEBRILE Hematogenous >>> penetrating Prematurity FPT Usually <1mo
Etiologic Agents
Aerobic/facultative anaerobes in 91% of cases Anaerobic - Clostridium Mycoplasma Rhodococcus Fungal agents --Scendosporium prolificans --Candida
Etiologic Agents: Aerobic/Facultative Anaerobes
Salmonella Strep zoo E. Coli Actinobacillus equili Staph aureus Borrelia
Dx Considerations
Hx, PE --assess entire P --Articular swelling, lameness, cellulitis +/- predisposing hx Synovial fluid analysis --cytology, gram stain --culture and sensitivity RADS
Dx Hx - Adults
ADULTS ALMOST NEVER FEBRILE Iatrogenic --Staph or Strep either post-op or post jt INJ Trauma Nearby IFX --foot abscess --cellulitis Idiopathic
Dx Sample Collection
Minimize blood contamination
Sample away from open wounds
Avoid cellulitis
Sample Types
Cytology/Gram Stain --EDTA, heparin Culture --Blood culture vials --Anaerobic/aerobic --NO ANTICOAG --fluid, fibrin, or synovium can be cultured Have dose of ABX ready to infuse
Synovial fluid analysis
Translucent yellow
Normal viscosity - mucin, HA –> string btw fingers
Cloudy fluid suggests >30,000 cells/uL
Normal Synovial Fluid
TP <2.0 to <2.5 g/dL
WBC <450 to <5000
Cell type <10% neutrophils
Synovial fluid - IFM
TP 2.5 to 4 g/dL
WBC 500 to 20,000
Cell type 10-50% neutrophils
Synovial fluid IFX
TP >4.0 g/dL
WBC >30,000/uL
Cell type >80% neutrophils
Serum Amyloid A
Not specific to sepsis
Synovial Fluid Cytology
Gram stain --ID bacteria in 25% --Rapid guidance for ABX selection Neutrophils --normally <10% synovial fluid --usually non-degenerate in early IFX -->80% usually always IFX'd --degenerate neutrophils ALWAYS bad
Dx: culture and sensitivity
No growth does not mean not infected
Single organism indicative of IFX
Pos culture correlates w/ decreased prof
Blood culture media increases likelihood of a positive culture
Dx - RADS
Radiographic lytic changes can occur in <1 week
–lag time
–most changes seen at 7-10d post IFX
Eval RADS for fx, gas opacity, lytic changes, FB
Systemic Eval
CBC, fibrinogen, SAA Fever Blood culture - foals Palpate - umbilicus, other jts US - umbilicus, lungs
Management Principles
- Eliminate IFX
- Establish drainage
- Restore normal synovial jt viscosity and fluid properties - jt milieu
- Eliminate IFX
Local ABX
Systemic ABX
Local ABX
IA
IV regional limb perfusion
Intraosseus perfusion
ABX-impregnated beads
Systemic ABXs
Penicillin + amikacin (foals) or gentamicin (adults)
Intraosseuous perfusion
More invasive than regional limb
Hole drilled into long bone and indwelling cannula is used to deliver ABX infusion - high ABX levels obtained
IA Anx
High levels directly into jt
Following high vol lavage
IA drains may be used to deliver abx +/- HA - CRI, clotting
IV Regional Limb Perfusion - Advantages
Mainstay of tx
Far greater ABX [ ] than systemic
Concentration remains higher than after systemic IV
Low dose may be effective - fewer SE
Effective tourniquet essential - heavy sedation or short IV ax
IV Regional Limb Perfusion - Disadvantages
Req functional tourniquet
Catheter site morbidity
–thrombosis, cellulitis
ABX Beads - non-absorbable
PMMA
Longest ABX elution (mo)
ABX beads - absorbable
Collagen
Plaster of Paris (PoP)
Bone cement - calcium phosphate
2) establish drainage - basics
Lavage-based physiological sln
Arthrotomy
Arthroscopy
Removal of necrotic tissues
2) establish drainage - more complicated
If significant amt of fibrin or thick synovial fluid or bony lesion, more aggressive drainage selected
–arthrotomy
–arthroscopy
Arthrotomies indicated in horses that do not respond rapidly to jt lavage
Arthroscopy vs arthrotomy
Experimentally both eliminate the IFX
–arthrotomy faster
Arthrotomy has increased risk of ascending IFX
–sterile bandaging critical
3) restoration of joint mileu
Anti-IFM - NSAIDS, HA Additional analgesia --epidural catheter --perineural anesthetic --IA anesthetics --bandaging --support CL limb -prevent laminitis
Sodium Hyaluronate (HA)
Anti IFM
Anti-adhesive
Bandaging
Reduces swelling, edema, and pain (jt pressure)
Protects arthrotomies
PT
During and after sepsis
Important to maintain ROM
Summary
Potential jt IFX = emergencies Early, aggressive tx best Foals have 50% prognosis vs 80% in adults Combo tx --eliminate IFX --establish drainage --restore jt mileu --Analgesia
