Review Question - QID 3357

This patient has clinical signs of infection with symptoms localized to the pelvis. The differential diagnosis of an infectious presentation with NWB in a child should include: discitis, sacroilitis, transient synovitis, septic hip, osteomyelitis, and Iliopsoas abscess. Further imaging is required to confirm the diagnosis. The radiographs are not consistent with a slipped capital femoral epiphysis.

An appropriate workup has been completed for septic arthritis, which is a surgical emergency and prompts drainage and debridement of the hip joint. The Kocher criteria for septic arthritis include fever>38.5 degrees centigrade, inability to bear weight, ESR>40 mm/h, and WBC count>12,000/ul. In this case, 2/4 of the criteria are positive (inability to bear weight & ESR>40mm/h), which indicates approximately a 40% likelihood of septic arthritis. Synovial fluid analysis is used to either confirm or reject the hypothesis of suspected septic arthritis; an aspiration of < 50,000 leukocytes per mL virtually rules out sepsis of the joint.

The paper by Beaupre et al discusses that iliac osteomyelitis is a rare cause of pediatric hip pain, and it can usually be effectively treated with antibiotics alone. Repeat aspiration of the joint is indicated if there is suspicion of a poorly done procedure, but it was image guided in this case. It is notable that a joint infection secondary to osteomyelitis is possible in the pediatric hip as result of the synovial reflections facilitating bacterial migration from the metaphysis to joint space. The synovial fluid analysis is critical in identifying presence or absence of joint infection.