title: Sonographic evaluation of hip effusion in children. Improved visualization with the hip in extension and abduction.
abstract: OBJECTIVE
  To assess the difference in the sonographic appearance of hip effusions when the hip was placed in the extended and abducted position as compared to a neutral position.
  
  
  METHODS
  Twenty-one consecutive children (aged 2-14 years) with hip pain or limping were examined for hip effusions by means of ultrasound. The capsule-femoral-neck distance, the presence of joint fluid, and the shape of the anterior capsule were compared in hips in slight extension and abduction with those in hips in a neutral position.
  
  
  RESULTS
  Of the 11 positive hip effusions, the maximal distance between the capsule and femoral neck was significantly larger (p < 0.005) in the extended and abducted hip position than in the neutral hip position, with a mean difference of 1.6 mm. Convex bulging of the anterior capsule was more confidently diagnosed in 3 hip effusions in the extended and abducted hip, and better visualization of fluid between the capsule and femoral neck was achieved in 4 joint in this posture.
  
  
  CONCLUSIONS
  The study demonstrated an improvement in the sonographic detection of hip effusion in the extended and abducted position compared to the neutral position.
authors.affiliation: Department of Diagnostic Radiology and Organ Imaging, Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong.
authors.forename: Y L
authors.initials: YL
authors.lastname: Chan
authors.forename: J C
authors.initials: JC
authors.lastname: Cheng
authors.forename: C
authors.initials: C
authors.lastname: Metreweli
mesh_terms: D000293:Adolescent; D018771:Arthralgia / Q000000981:diagnostic imaging; D002648:Child; D002675:Child, Preschool; D005122:Exudates and Transudates / Q000000981:diagnostic imaging*; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D007383:Intermittent Claudication / Q000000981:diagnostic imaging; D008297:Male; D016059:Range of Motion, Articular; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation