Septic [Acute Suppurative] Arthritis Flashcards
Adult vs Pediatric (8 cards)
Epidemiology [Adults]
most commonly affected joints in descending order:
- Knee [> 50 % cases]
- Hip
- Shoulder
- Elbow
- Ankle
- Sternoclavicular joints [common in IV drug users, Staph aureus most common pathogen]
Risk Factors:
- Age > 80 years old
- Diabetes, Rheumatoid Arthritis, Cirrhosis, HIV
- History of Crystal arthropathy
- IV drug user
- Endocarditis or recent bacteremia
- Recent joint surgery
It is an inflammatory joint infection usually with bacterial origin
Pediatric cases, Hip joint involvement in 35% of cases, risks include prematurity-C section-NICU treatment-Catheter usage or heel puncture leading to transient bacteremia
Etiology
Bacterial seeding leads to joint infection:
- Bacteremia
- Direct inoculation [trauma or surgery]
- Contiguous spread from adjacent Osteomyelitis
Septic arthritis causes irreversible cartilage destruction in an involved joint [injury can occur by 8 hours] due to proteolytic enzyme release from PMNs
Pediatric cases - Direct inoculation, Hematogenous seeding [Upper respiratory infection], Osteomyelitis extention
Classification [based on Organism]
Staph species:
- Staph aureus [> 50% cases]
- MRSA
- Staph epidermis
Neisseria Gonorrhea:
- In otherwise healthy, sexually active adolescents and young adutls
- Bacteremic infection leading to septic arthritis [Arthritis-Dermatitis syndrome; localized septic arthritis]
Gram negative bacilli:
- Ecoli, Klebsiella, Proteus, Enterobacter
- In neonates, IV drug users, Elderly, Immunocompromised patients with diabetes
Strep species:
- Strep pyogenes [most common]
- Group B
Pseudomonas Aeruginosa:
- Seen in patients with history of IV drug abuse
Pediatric Cases - HACEK organsism [Kingella most common in all ages], Staph aureus, Neisseria
Presentation
Sx:
- Pain in affected side
- Acute onset
- Fevers in 60% cases
Physical Exam:
- Inspection = Erythema, Effusion, Extremity tends to be in position of max joint volume [Hip in FABER position]
- Palpation = Warmth, Tender
- Motion = Inability or refusal to bear weight on affected side; Inability to tolerate PROM
Imaging Obtained
- Xrays [AP and Lateral of affected joint | may show joint space widening, effusion or Periarticular osteopenia]
- Ultrasound [Confirms joint effusion in large joints like hips, guide for aspiration study]
- MRI [detects joint effusion, may also detect osteomyelitis in involved bone]
Labs needed
Serum labs:
- WBC > 10k cells/ml with left shift
- ESR > 30mm/hr [may be normal if early]
- CRP > 1mg/dl [most helpful and best way to judge efficacy of treatment, normalizes within 1 week of treatment]
Joint Fluid Aspirate:
- GOLD standard for treatment and allows direct antibiotic tx
- Analysed for Cell count with differential, Gram stain, Culture, Glucose levels, Crystal analysis
- Characteristically = Fluid cloudy or purulent; Cell count WBC > 50k diagnostic but can be lower [false negative if antibiotics given within 24 hours of arthrocentesis]; Glucose less than 60% of serum levels [Bacteria use glucose]; Negative string sign [synovial fluid less viscous than normal synovial fluid]
Saline Load test:
- To determine if wound near a joint communicates with the joint space
Differential Dx
Crystal arthropathy
- Gout
- Pseudogout
Cellulitis
Bursitis [prepatellar]
Treatment
Non-operative:
- Gonococcal septic arthritis using Ceftriaxone/Fluoroquinolones + Aspiration
Operative: IV antibiotics, Irrigation and Drainage of joint
- Orthopedic emergency because of irreversible cartilage damage within 8 hours of arthritis development
- IV antibiotics [Emperic before cultures arrive = Young healthy adults assume Staph aureus/Neisseria | Immunocompromised patients assume Staph aureus/Pseudomonas ; Transition to organism specific onces cultures and sensitivities known]
- Open or Arthroscopic approach
- Irrigation involves removal of all fluid and irrigating joint
- Debridement [Synovectomy if needed]
- Obtain more fluid and tissues for cultures
