Septic Arthritis in Children

Background

• Septic arthritis in children, the pathologic invasion of the synovium or joint space, represents a medical emergency and requires immediate diagnosis and treatment.
• Infection most commonly occurs via hematogenous spread, though contiguous spread and direct inoculation also occur.
• 90% of cases are monoarticular, with knees and hips the most commonly involved joints.
• Staphylococcus aureus is the most frequently isolated pathogen, but a wide array of bacteria, fungi, and viruses have been implicated.

Evaluation

• Septic arthritis in children commonly presents with immobility and joint dysfunction (including limited range of motion and gait disturbance), fever, swelling, redness, irritability, and malaise.
• Neonates and very young children may not present with systemic symptoms, and instead present with refusal to eat, crying, or discomfort during movement of the joint.
• Findings on blood tests may include elevated white blood cell count, C-reactive protein, and erythrocyte sedimentation rate, with blood cultures positive in about 20% of patients.
• Synovial fluid analysis is key to diagnosis and guiding antibiotic therapy.
  • Fluid should be analyzed for glucose, cell count, Gram stain, and culture.
  • Addition of polymerase chain reaction studies to culture may improve diagnostic yield.

Management

• Treatment often requires a multidisciplinary team.
• Empiric antibiotic therapy should begin as soon as cultures are obtained and should not await final culture results, with initial therapy guided by clinical findings and local epidemiology.
  • In neonates, regimens include
    • antistaphylococcal agent (oxacillin, nafcillin, cefazolin) plus cefotaxime or gentamicin.
    • or if methicillin-resistant Staphylococcus aureus (MRSA) suspected, vancomycin or clindamycin (if local antibiogram confirms high susceptibility) plus cefotaxime or gentamicin.
  • In children < 5 years old regimens include
    • antistaphylococcal penicillin (nafcillin or oxacillin) or first-generation cephalosporin (cefazolin).
    • or if MRSA suspected, vancomycin or clindamycin (if local antibiogram confirms high susceptibility) plus a third generation cephalosporin (if K. kingae also suspected use ceftriaxone or cefotaxime as third generation cephalosporin or add cefazolin).
  • In children > 5 years old regimens include
    • antistaphylococcal penicillin (nafcillin or oxacillin) or first-generation cephalosporin (cefazolin)
    • or if MRSA suspected, vancomycin or clindamycin (if local antibiogram confirms high susceptibility).
• Adjust antibiotic therapy based on final culture results.
• Uncomplicated septic arthritis is usually treated with 2-7 days of IV antibiotics followed by 2-4 weeks of oral therapy. Approximately 10% of children require more prolonged IV therapy.
• Adjunctive corticosteroid therapy (such as dexamethasone 0.6 mg/kg/day in 3-4 doses IV) may be considered early in the course of therapy, but should be used cautiously in children with signs or symptoms of sepsis or systemic inflammatory response syndrome (SIRS).
• Joint aspiration(s) may be sufficient in patients diagnosed early with uncomplicated infections in superficial joints.
• Arthroscopic irrigation and debridement of septic arthritis of the knee may be considered.
• Urgent surgical decompression of joints may be required in patients with large collections, thick pus, joint loculations, or pus evacuating into surrounding soft tissue, or in patients with hip arthritis due to femoral head being at risk of avascular necrosis.
• Patients should be followed at least 6 weeks after symptom resolution but ideally for a year, as multiple complications may occur.