IMAGING INFANT HIPS AND THE LIMPING CHILD

“Commonly Requested but Misunderstood Studies ” with a discussion on imaging infant hips and the limping child. The most common reason for hip imaging in the newborn is hip dysplasia. Risk factors include being female, breech presentation, firstborn and family history of hip dysplasia (1). Due to patient size and lack of epiphyseal ossification, ultrasound is the initial study of choice for possible hip dysplasia in children less than 6 months of age. After 6 months, radiographs of the pelvis are indicated. In children with a limp or hip pain, the appropriate study (plain radiographs vs. ultrasound vs. MRI vs. bone scan) is strongly determined by the clinical history and physical exam. Specifically, one must know: (1) The child’s age (2) If a fever is present, how high (3) If there is hip pain with manipulation (4) Does the child refused to bear weight and (5) If there are positive lab inflammatory markers (ESR, CRP) and if so, how positive? Using this information, it may be possible to distinguish viral versus bacterial joint infection versus osteomyelitis and determine the appropriate imaging. Children with transient (toxic) synovitis, are generally 3 to 8 years of age, present with a limp and less often refusal to bear weight. Symptoms usually resolve spontaneously within a few days. A low grade fever may be present or the child may be afebrile. Moderate pain is associated with passive motion of the hip on physical exam. NO IMAGING or HIP ASPIRATION is needed in children with toxic synovitis although many will have hip effusions. If symptoms persist, pelvic radiographs may be useful to evaluate for avascular necrosis. Children with septic arthritis present at any age with a severe limp or inability to bear weight, fever, and guarding or severe pain with passive motio