title: Hip joint fluid: detection and distribution at MR imaging and US with cadaveric correlation.
abstract: OBJECTIVE
  To define the magnetic resonance (MR) imaging appearance of a hip effusion.
  
  
  METHODS
  Fifty-two asymptomatic hips in 26 volunteers aged 20-37 years and five fractured hips were imaged at 1.5 T with T2-weighting in three planes. Images were computer digitized and analyzed for hip fluid volume and visually assessed for the presence and width of fluid pockets (in millimeters) seen in the acetabular notch; recesses anterior, posterior, and lateral to the femoral head; and recesses anterior, posterior, and medial to the femoral neck. Cadaveric hips were also injected with graduated amounts of saline (1-20 mL), and sequential MR and ultrasound images were obtained.
  
  
  RESULTS
  Computer analysis yielded an average fluid volume of 2.7 mL (range, 0.7-5.6 mL) in asymptomatic and 6.1 mL (range, 1.7-11.6 mL) in symptomatic hips. The mean difference between the right and left hips was 0.8 mL (range, 0.0-2.9 mL). Discrete fluid pockets, sometimes measuring greater than 5 mm in width, were commonly seen in asymptomatic hips. Distention of the capsule by at least 5 mm along the length of the femoral neck was almost always seen after injection of 5 mL of saline and was consistently seen after injection of 10 mL of saline into cadaveric hips.
  
  
  CONCLUSIONS
  Fluid adjacent to the entire length of the femoral neck, measuring at least 5 mm in width, is compatible with a joint effusion.
authors.affiliation: Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA 19107, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Moss
authors.forename: M E
authors.initials: ME
authors.lastname: Schweitzer
authors.forename: J A
authors.initials: JA
authors.lastname: Jacobson
authors.forename: J
authors.initials: J
authors.lastname: Brossmann
authors.forename: J V
authors.initials: JV
authors.lastname: Lombardi
authors.forename: S M
authors.initials: SM
authors.lastname: Dellose
authors.forename: J R
authors.initials: JR
authors.lastname: Coralnick
authors.forename: K N
authors.initials: KN
authors.lastname: Standiford
authors.forename: D
authors.initials: D
authors.lastname: Resnick
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000473:pathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging / Q000473:pathology; D005272:Femur Neck / Q000000981:diagnostic imaging / Q000473:pathology; D006620:Hip Fractures / Q000000981:diagnostic imaging / Q000473:pathology; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007270:Injections, Intra-Articular; D017746:Joint Capsule / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D012965:Sodium Chloride / Q000008:administration & dosage; D013582:Synovial Fluid / Q000000981:diagnostic imaging*; D014463:Ultrasonography
chemical_list: D012965:Sodium Chloride