Arthritis, Pyogenic

Key Features

• Source varies according to the child's age

  • Infantile pyogenic arthritis often develops from adjacent osteomyelitis

  • In older children, it presents as an isolated infection, usually without bony involvement

  • In teenagers, an underlying systemic disease or an organism that has an affinity for joints (eg, Neisseria gonorrhoeae) may be present

• The most frequent infecting organisms similarly vary with age

  • Group B Streptococcus and Staphylococcus aureus in those younger than 4 months

  • Haemophilus influenzae type b (if unimmunized) and S aureus in those aged 4 months to 4 years

  • S aureus and Streptococcus pyogenes in older children and adolescents

  • Streptococcus pneumoniae and Neisseria meningitis are occasionally implicated, and N gonorrhoeae is a cause in adolescents

  • Kingella kingae is a gram-negative bacterium that is increasingly recognized as a cause of pyarthrosis (and, occasionally, osteomyelitis) in children younger than 5 years

Clinical Findings

• In infants,

  • Paralysis of the limb due to inflammatory pseudoparalysis may be evident

  • Infection of the hip joint should be suspected if decreased abduction of the hip is present in an infant who is irritable or feeding poorly

  • A history of umbilical catheter treatment in the newborn nursery should alert the physician to the possibility of pyogenic arthritis of the hip

• In older children,

  • Fever

  • Malaise

  • Vomiting

  • Restriction of motion

  • Joint swelling, warmth, erythema, tenderness

Diagnosis

• A joint effusion may accompany osteomyelitis in the adjacent bone, but a white cell count exceeding 50,000/μL in the joint fluid indicates a purulent infection involving the joint

• Generally, spread of infection is from bone into a joint, but unattended pyogenic arthritis may also affect adjacent bone

• Erythrocyte sedimentation rate (ESR) is often above 50 mm/h

• Early distention of the joint capsule is nonspecific and difficult to measure by plain radiograph

• In infants with unrecognized pyogenic arthritis, dislocation of the joint may follow within a few days as a result of distention of the capsule by pus

• Destruction of the joint space, resorption of epiphysial cartilage, and erosion of the adjacent bone of the metaphysis occur later

• Bone scan shows increased flow and increased uptake about the joint

• MRI and ultrasonography are useful adjuncts for detecting joint effusions, which can be helpful in assessing potential joint sepsis

Treatment

• Surgical drainage followed by the appropriate antibiotic therapy

• Antibiotics can be selected based on the child's age and results of the Gram stain and culture of aspirated pus

  • Reasonable empiric therapy in infants and young children is nafcillin or oxacillin plus a third-generation cephalosporin

  • An antistaphylococcal agent alone is usually adequate for children older than 5 years, unless gonococcal or meningococcal infection is suspected.

  • Clindamycin or vancomycin may be needed if methicillin-resistant S aureus is suspected or isolated

• Duration of antibiotic therapy

  • For staphylococcal infections, a minimum of 3 weeks of therapy and until examination and inflammatory markers are normal

  • For other ...