Pediatric emergency medicine trisk 1164 1164

come to medical attention after minor trauma New-onset periarticular swelling and pain immediately after acute trauma suggests ligamentous or other soft tissue injury Monoarthritis In the absence of trauma, monoarthritis of the hip may represent a true orthopedic emergency Septic hips require operative drainage to prevent osteonecrosis and the most important prognostic factor is the length of delay in operative management Unlike most other causes of fever and arthritis, septic arthritis involves only a single joint in more than 90% of affected children; 80% of these are hip, knee, or ankle infections The absence of fever does not preclude the diagnosis; just 60% to 70% of children with septic arthritis are febrile at presentation A child with septic arthritis of the hip will typically maintain external rotation of the hip, resist even the slightest range of motion and be unable to ambulate In fact, if the child allows full range of motion, the diagnosis is highly unlikely Neonates, on the other hand, will often present with thigh swelling, pseudoparalysis, and external rotation at the hip A child with acute onset of monoarthritis of the hip or any other large joint, marked by an effusion and severely restricted range of motion, with or without fever, needs an arthrocentesis The study may be performed with bedside ultrasound guidance or by orthopedists or radiology specialists The synovial fluid should be analyzed for cell count and differential, Gram stain, and culture In two large series, about half of the children with septic arthritis of the hip had negative synovial fluid cultures In these cases, children with synovial fluid WBC counts greater than 50,000 per mm3 and positive blood cultures were presumed to have septic arthritis and managed accordingly Staphylococcus aureus is the most common infecting agent for older children, whereas group B Streptococcus and gram-negative enteric organisms must also be considered in neonates In recent years, clinicians are encountering a greater prevalence of community-associated methicillin-resistant S aureus (MRSA) as a causative agent Kingella kingae , a gram-negative coccobacillus, must be considered when evaluating a preschoolaged child, especially if the child has a chronic medical condition In contrast to septic arthritis, children with transient synovitis of the hip usually appear well, are afebrile, are often able to bear weight but have a limp, and allow almost complete range of motion of the affected joint A prospective study of over 150 children presenting with an irritable hip found that just 2% of children had septic arthritis if each of these four risk factors were absent: Fever >38.5°C, refusal to bear weight, ESR >40 mm/hr, and WBC >12,000 cells/mm3 Subsequent studies have had mixed results validating these criteria and it is likely